6. Scanning a System

6.1. Using the Task Wizard for a Scan


gb_video The steps for using the wizard are briefly explained in a video.


The task wizard can configure and start a scan with minimal user input.

  1. Select Scan Management in the menu panel.

  2. Click + Prepare New Scan Task with Wizard.

    → An information message is displayed.

  3. Click Let’s go!.

    Note

    If the message should not be displayed again, activate the checkbox Do not show again before clicking Let’s go!.

  4. Enter the name for the task in the input box Task name (see Fig. 6.1).

    _images/scan_wizard_1.png

    Fig. 6.1 Using the wizard

  5. Optional: enter a description for the task in the input box Description (optional).

  6. Select the scan configuration.

    Note

    The scan configuration Analysis [standard] is recommended.

  7. Click Save and Continue.

  1. Select an already available target from the list.

    or

  1. Click + Create New Target to create a new target.

    Tip

    For the information to enter in the input boxes see Chapter 6.2.1.

  2. Click Save and Continue.

  3. Optional: select already available credentials for Microsoft Windows login (SMB), SSH, or VMware ESXi from the list.

    or

  1. Optional: click + Create New Login Credentials to create new credentials.

    Tip

    For the information to enter in the input boxes see Chapter 6.3.2.1.

  2. Click Save and Continue.

  3. Optional: select an already available schedule from the list.

    or

  1. Optional: click + Create New Schedule to create a new schedule.

    Tip

    For the information to enter in the input boxes see Chapter 6.4.1.

  2. Click Save and Continue.

    Note

    If an external target was chosen and the host(s) have not been validated yet, Request Host Validation is displayed for the host(s) (see Fig. 6.2).

    _images/scan_wizard_2.png

    Fig. 6.2 Host(s) not validated yet

  3. To carry out the host validation, click Request Host Validation.

    → The contacts for the configured host(s) are collected from RIPE NCC. For more information see Chapter 6.2.2.

    When this process is finished, an overlay displays the found contact (see Fig. 6.3).

    Note

    If no contact was found, the hosts have to be checked manually by the vMSP’s security team.

  4. Select the contact person from the list.

    or

  1. Activate the checkbox Manual check by the security team.

    _images/host_validation_2.png

    Fig. 6.3 Selecting contact for the host validation

  2. Click Request Host Validation.

    → An e-mail is sent to the contact person or the security team. The status of the host validation is displayed on the page Targets.

  3. Click Prepare Scan.

    → The page Scan Management is opened.

  4. In the row of the created task click start.

For the status of a task see Chapter 6.7.

Tip

The report of a task can be displayed as soon as the task has been started by clicking file for the respective task on the page Scan Management.

For reading, managing and downloading reports see Chapter 7.

As soon as the status changes to Done the complete report is available. At any time the intermediate results can be reviewed (see Chapter 7.1).

Note

It can take a while for the scan to complete. The page is refreshing automatically if new data is available.

6.2. Configuring a Simple Scan Manually

Generally speaking the GCS can use two different approaches to scan a target:

  • Simple scan

  • Authenticated scan using local security checks (see Chapter 6.3)

The following steps have to be executed to configure a simple scan:

  • Creating a target (see Chapter 6.2.1)

  • Validating the host(s) (see Chapter 6.2.2) or creating a gateway (see Chapter 6.2.3)

  • Creating a task (see Chapter 6.2.4)

  • Starting the task (see Chapter 6.2.5)

6.2.1. Creating a Target

The first step is to define a scan target as follows:

  1. Select Targets (category Scan Configuration) in the menu panel.

  2. Click External Targets or Internal Targets depending on which type of target should be created.

  3. Create a new target by clicking + Create External Target or + Create Internal Target.

    Note

    If an external target is created, a host validation is necessary before it can be scanned (see Chapter 6.2.2).

    If an internal target is created, a gateway has to be used for scanning (see Chapter 6.2.3).

_images/target_new.png

Fig. 6.4 Creating a new target

  1. Define the target (see Fig. 6.4).

  2. Click Create Target.

The following information can be entered:

Target name

The name can be chosen freely. A descriptive name should be chosen if possible.

Description (optional)

The optional comment allows specifying background information. It simplifies understanding the configured targets later.

Hosts

Manual entry of the hosts that should be scanned, separated by commas.

Note

The IP address or the host name is required. In both cases it is necessary that the GCS can connect to the system. If using the host name, the GCS must also be able to resolve the name.

For entering the following options are available:

  • Single IP address, e.g., 192.168.15.5

  • Host name, e.g., mail.example.com

  • IPv4 address range in long format, e.g., 192.168.15.5-192.168.15.27

  • IPv4 address range in short format, e.g., 192.168.55.5-27

  • IPv4 address range in CIDR notation, e.g., 192.168.15.0/24 1 (at most 4096 IP addresses)

Multiple options can be mixed.

Excluded Hosts (Optional)

Manual entry of the hosts that should be excluded from the list mentioned above, separated by commas.

The same specifications as for Hosts apply.

Alive test

This options specifies the method to check if a target is reachable. Options are:

  • TCP ack service

  • ICMP

  • Consider alive

  • TCP syn service

Port list

Port list used for the scan (see Chapter 6.9).

Login credentials SSH

Selection of a user that can log into the target system of a scan if it is a Linux or Unix system. This allows for an authenticated scan using local security checks (see Chapter 6.3).

Login credentials SMB

Selection of a user that can log into the target system of a scan if it is a Microsoft Windows system. This allows for an authenticated scan using local security checks (see Chapter 6.3).

Login credentials ESXi

Selection of a user that can log into the target system of a scan if it is a VMware ESXi system. This allows for an authenticated scan using local security checks (see Chapter 6.3).

6.2.2. For External Targets: Validating the Hosts

If an external target is created, the defined hosts have to be validated. Scanning targets without host validation is not possible.

A host can either be validated by the person responsible for the host or by the security team of the vMSP.

The responsible person – if available – is obtained from RIPE NCC. RIPE NCC is the Regional Internet Registry (RIR) for Europe, the Middle East and parts of Central Asia and allocates and registers IP address ranges.

  1. Select Targets (category Scan Configuration) in the menu panel.

    → If the validation has not been completed yet, verification_pending is displayed in the column Verified.

  2. In the row of the target click assignment.

  3. Click Request Host Validation (see Fig. 6.5).

    _images/host_validation_1.png

    Fig. 6.5 Requesting the host validation

    → The contacts for the configured host are collected from RIPE NCC.

    When this process is finished, an overlay displays the found contact (see Fig. 6.6).

    Note

    If no contact was found, the hosts have to be checked manually by the vMSP’s security team.

  4. Select the contact person from the list.

    or

  1. Activate the checkbox Manual check by the security team.

    _images/host_validation_2.png

    Fig. 6.6 Selecting contact for the host validation

  2. Click Request Host Validation.

    → An e-mail is sent to the contact person or the security team.

    Note

    By clicking Reset Contact Selection the selected contact is rejected.

    If the hosts are validated, hosts_verified is displayed in the column Verified on the page Targets.

    If the host validation is rejected, verification_rejected is displayed in the column Verified on the page Targets.

6.2.3. For Internal Targets: Creating a Gateway

If an internal target in the customer’s network should be scanned, a gateway has to be used.

Note

The gateway can be imported to Microsoft Hyper-V or VMware ESXi.

A gateway can be created as follows:

  1. Select Gateways (category Scan Configuration) in the menu panel.

  2. Select the desired virtual environment in the drop-down list Download and click report_download.

  3. Import the gateway to the virtual environment.

  4. Start the gateway in the virtual environment.

  5. After the boot process is completed, the login prompt is shown. The default login information is:

    • User: admin

    • Password: admin

    → The gateway administration menu is opened.

  6. Select Gateway configuration and press Enter.

  7. Select Set web password and press Enter.

  8. Enter the password twice and press Tab (see Fig. 6.7).

    Note

    The password has to fulfill the following criteria:

    • At least 8 characters

    • Contains upper and lower cases

    • Contains at least one special character

    • Contains at least one number

    _images/gateway_6.png

    Fig. 6.7 Setting the password for the gateway web interface

  9. Press Enter.

  10. Select Save changes and press Enter.

    → A message informs that the gateway was configured successfully.

  11. Press Enter to close the message.

  12. Select Network configuration and press Enter.

    Note

    For all configuration options see Chapter 6.6.2.

  13. Note the IP address of the gateway (see Fig. 6.8). It is needed for accessing the gateway web interface.

    _images/gateway_2.png

    Fig. 6.8 IP address of the gateway

  14. On the platform click + Create New Gateway.

  15. Enter a textual description of the gateway’s location in the input box Location (see Fig. 6.9).

    _images/gateway_3.png

    Fig. 6.9 Creating a new gateway

  16. Optional: enter a description for the gateway in the input box Description.

  17. Enter a free IP address from the network that should be scanned including the prefix length in the input box IP address/network.

    Note

    The entered IP address has to differ from the IP address of the gateway.

    Note

    By default, MAC-NAT is enabled.

  18. If MAC-NAT does not work, click Advanced, deactivate the checkbox Use MAC-NAT and configure the settings displayed on the page Gateways (see Fig. 6.10).

    _images/gateway_without_MAC_NAT.png

    Fig. 6.10 Advanced virtual environment settings

    Note

    If a network is to be scanned in which the scanner is not located, network routing can be used.

  19. Click + Create New Route.

  20. Define the route by entering the network and the gateway located in the network in the respective input boxes.

  21. Enter the metric information in the input box Metric.

    The metric is important if there are multiple routes for the same target network. In this case, the best route is the one with the smallest metric value.

  22. Click Save.

    → The route is displayed in the table.

  23. Click New Gateway.

    → The gateway is created and displayed on the page Gateways.

Registering the Gateway

The gateway has to be registered either via gateway web interface or via gateway administration menu (CLI).

The registration via gateway web interface is carried out as follows:

  1. In the row of the gateway click edit.

  2. Select WEB.

  3. Click Copy to Clipboard to copy the API key.

  4. Open the web browser and enter the following URL: https://<ip>. Replace <ip> with the IP address of the gateway (see step 13).

  5. Log in using the user name admin and the password defined in steps 6 – 9.

  6. Select Settings in the menu panel.

  7. Paste the API key in the input box API-Key.

  8. Click Save.

    → On the page Gateways on the platform, the column Status displays CONNECTED (see Fig. 6.11).

    _images/gateway_4.png

    Fig. 6.11 Connecting the gateway

The registration via gateway administration menu (CLI) is carried out as follows:

  1. In the row of the gateway click edit.

  2. Select CLI.

  3. Note the token and the host address.

  4. In the CLI, select Gateway configuration and press Enter.

  5. Select Enter connection token (Optional) and press Enter.

  6. Enter the host address and the token in the respective input fields (see Fig. 6.12).

    _images/gateway_8.png

    Fig. 6.12 Connecting the gateway

  7. Press Tab and Enter.

    → On the page Gateways on the platform, the column Status displays CONNECTED (see Fig. 6.11).

6.2.4. Creating a Task

The next step is to create a task.

The GCS control the execution of a scan using tasks. These tasks can be repeated regularly or run at specific times (see Chapter 6.4).

A task can be created as follows:

  1. Select Scan Configuration in the menu panel.

  2. Create a new task by clicking + Create New Task.

  3. Define the task (see Fig. 6.13).

    _images/task_new.png

    Fig. 6.13 Creating a new task

  4. Click Create Task.

    → The task is created and displayed on the page Scan Configuration.

The following information can be entered:

Name

The name can be chosen freely. A descriptive name should be chosen if possible.

Comment

The optional comment allows for the entry of background information. It simplifies understanding the configured task later.

Select target

Select a previously configured target from the drop-down list (see Chapter 6.2.1).

Schedule

Select a previously configured schedule from the drop-down list (see Chapter 6.4). The task can be run once or repeatedly at a predetermined time, e.g., every Monday morning at 6:00 a.m.

Selecting a schedule is optional. If no schedule should be used, select Do not use a schedule.

Scan configuration

The GCS come with five pre-configured scan configurations (see Chapter 6.8).

The following option is only visible if an internal target is selected:

Gateway

Select a previously configured gateway from the drop-down list (see Chapter 6.2.3).

6.2.5. Starting the Task


gb_video The scan management including how to start scans is briefly explained in a video.


Select Scan Management in the menu panel. In the row of the desired task, click start.

→ The scan is running. For the status of a task see Chapter 6.7.

Tip

The report of a task can be displayed as soon as the task has been started by clicking file. For reading, managing and downloading reports see Chapter 7.

As soon as the status changes to Done the complete report is available. At any time the intermediate results can be reviewed (see Chapter 7.1).

Note

It can take a while for the scan to complete. The page is refreshing automatically if new data is available.

6.3. Configuring an Authenticated Scan Using Local Security Checks

An authenticated scan can provide more vulnerability details on the scanned system. During an authenticated scan the target is both scanned from the outside using the network and from the inside using a valid user login.

During an authenticated scan the GCS log into the target system in order to run local security checks (LSC). The scan requires the prior setup of user credentials. These credentials are used to authenticate to different services on the target system. In some circumstances the results could be limited by the permissions of the users used.

The VTs in the corresponding VT families (local security checks) will only be executed if the GCS were able to log into the target system. The local security check VTs in the resulting scan are minimally invasive.

The GCS only determine the risk level but do not introduce any changes on the target system. However, the login by the GCS is probably logged in the protocols of the target system.

The GCS can use different credentials based on the nature of the target. The most important ones are:

  • SMB

    On Microsoft Windows systems the GCS can check the patch level and locally installed software such as Adobe Acrobat Reader or the Java suite.

  • SSH

    This access is used to check the patch level on Unix and Linux systems.

  • ESXi

    This access is used for testing of VMware ESXi servers locally.

6.3.1. Advantages and Disadvantages of Authenticated Scans

The extent and success of the testing routines for authenticated scans depend heavily on the permissions of the used account.

On Linux systems an unprivileged user is sufficient and can access most interesting information while especially on Microsoft Windows systems unprivileged users are very restricted and administrative users provide more results. An unprivileged user does not have access to the Microsoft Windows registry and the Microsoft Windows system folder \windows which contains the information on updates and patch levels.

Local security checks are the most gentle method to scan for vulnerability details. While remote security checks try to be least invasive as well, they may have some impact.

Simply stated an authenticated scan is similar to a Whitebox approach. The GCS have access to prior information and can access the target from within. Especially the registry, software versions and patch levels are accessible.

A remote scan is similar to a Blackbox approach. The GCS use the same techniques and protocols as a potential attacker to access the target from the outside. The only information available was collected by the GCS themselves. During the test the GCS may provoke malfunctions to extract any available information on the used software, e.g., the scanner may send a malformed request to a service to trigger a response containing further information on the deployed product.

During a remote scan using the scan configuration Analysis [Standard] all remote checks are safe. The used VTs may have some invasive components but none of the used VTs try to trigger a defect or malfunction in the target (see example below). All VTs with very invasive components or which may trigger a denial of service (DoS) are automatically excluded from the test.

Example for an Invasive VT

An example for an invasive but safe VT is the Heartbleed VT. It is executed even if VTs that may cause damage to the host system are disabled because the VT does not have any negative impact on the target.

The VT is still invasive because it tests the memory leakage of the target. If the target is vulnerable, actual memory of the target is leaked. The GCS do not evaluate the leaked information. The information is immediately discarded.

6.3.2. Using Credentials

Credentials for local security checks are required to allow VTs to log into target systems, e.g., for the purpose of locally checking the presence of all vendor security patches.


gb_video The steps for creating and using credentials are briefly explained in a video.


6.3.2.1. Creating Credentials

New credentials can be created as follows:

  1. Select Login Credentials (category Scan Configuration) in the menu panel.

  2. Create new credentials by clicking + Create New Login Credentials.

  3. Define the credentials (see Fig. 6.14).

    _images/credentials_new.png

    Fig. 6.14 Creating new credentials

  4. Click Create Credentials.

The following details of the credentials can be defined:

Note

If the details contain German umlauts, the login does not work. The umlauts have to be replaced as follows:

  • “ß” → “ss”

  • “ä” → “a”

  • “ö” → “o”

  • “ü” → “u”

Credentials name

Definition of the name. The name can be chosen freely.

Description (optional)

An optional comment can contain additional information.

Login & password/Login, passphrase & private key

Selection of the credential type.

Depending on the selected type, further options are shown:

Login & password
  • Login

    Definition of the login name used by the GCS to authenticate on the scanned target system.

  • Password

    Definition of the password used by the GCS to authenticate on the scanned target system.

Login, passphrase & private key
  • Login

    Definition of the login name used by the GCS to authenticate on the scanned target system.

  • Passphrase

    Definition of the passphrase of the private SSH key.

  • Private key

    Upload of the private SSH key by clicking FILE SELECTION.

    An uploaded file can be deleted by clicking trashcan.

6.3.2.2. Managing Credentials

All existing credentials can be displayed by selecting Login Credentials in the menu panel.

For all credentials the following information is displayed:

Name

Name of the credentials.

Login Name

User name for the credentials.

Comment

Optional additional information about the credentials.

For all credentials the following actions are available:

  • edit Edit the credentials.

  • trashcan Delete the credentials. Only credentials which are currently not used can be deleted.

6.3.3. Requirements on Target Systems with Microsoft Windows

6.3.3.1. General Notes on the Configuration

  • The remote registry service must be started in order to access the registry.

    This is achieved by configuring the service to automatically start up. If an automatic start is not preferred, a manual startup can be configured. In that case the service is started while the system is scanned by the GCS and afterwards it is disabled again. To ensure this behaviour the following information about LocalAccountTokenFilterPolicy must be considered.

  • It is necessary that for all scanned systems the file and printer sharing is activated. If using Microsoft Windows XP, take care to disable the setting Use Simple File Sharing.

  • For individual systems not attached to a domain the following registry key must be set:

    HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System\
    DWORD: LocalAccountTokenFilterPolicy = 1
    
  • On systems with domain controller the user account in use must be a member of the group Domain Administrators to achieve the best possible results. Due to the permission concept it is not possible to discover all vulnerabilities using the Local Administrator or the administrators assigned by the domain. Alternatively follow the instructions in Chapter 6.3.3.2.

  • Should a Local Administrator be selected – which it explicitly not recommended – it is mandatory to set the following registry key as well:

    HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System\
    DWORD: LocalAccountTokenFilterPolicy = 1
    
  • Generated install package for credentials: The installer sets the remote registry service to auto start. If the installer is executed on a domain controller, the user account will be assigned to the group BUILTIN/Administrators (SID S-1-5-32-544).

  • An exception rule for the GCS on the Microsoft Windows firewall must be created. Additionally, on XP systems the service File and Printer Sharing must be set to enabled.

  • Generated install package for credentials: During the installation the installer offers a dialog to enter the IP address of the GCS. If the entry is confirmed, the firewall rule is configured. The service File and Printer Sharing will be enabled in the firewall rules.

6.3.3.2. Configuring a Domain Account for Authenticated Scans

For authenticated scans of Microsoft Windows target systems, it is highly recommended to use a domain account with a domain policy that grants local administrator privileges. This has several advantages:

  • A domain policy only needs to be created once and can then be applied or revoked for different user accounts.

  • Editing the Microsoft Windows registry locally is no longer required. User administration is thus centralized, which saves time in the long term and reduces possible configuration errors.

  • From a vulnerability assessment perspective, only a domain account allows for the detection of domain-related scan results. These results will be missing if using a local user account.

  • There are also several security advantages to using a domain account with the domain policy recommended by Greenbone Networks: the corresponding user may not log in locally or via the remote desktop protocol (RDP), limiting possible attack vectors. Additionally, the user credentials are secured via Kerberos, while the password of a local user account is at much greater risk of being exposed through exploits.

In order to use a domain account for host based remote audits on a Microsoft Windows target, the following configuration must be made under Windows XP Professional, Windows Vista, Windows Server 2003, Windows Server 2008, Windows Server 2012, Windows Server 2016, Windows 7, Windows 8, Windows 8.1 or Windows 10. The system must also be part of the domain.

Creating a Security Group

  1. Log into a domain controller and open Active Directory Users and Computers.

  2. Select Action > New > Group in the menu bar.

  3. Enter Greenbone Local Scan in the input box Name.

  4. Select Global for Group Scope and Security for Group Type.

  5. Add the account used for the local authenticated scans by the GCS under Microsoft Windows to the group.

  6. Click OK.

Creating a Group Policy Object (GPO)

  1. In the left panel open the console Group Policy Management.

  2. Right click Group Policy Objects and select New.

  3. Enter Greenbone Local SecRights in the input box Name (see Fig. 6.15).

    _images/win_group_policy.png

    Fig. 6.15 Creating a new Microsoft Windows group policy object for Greenbone Networks scans

  4. Click OK.

Configuring the Policy

  1. Click the policy Greenbone Local SecRights and select Edit.

  2. Select Computer Configuration > Policies > Windows Settings > Security Settings in the left panel.

  3. Click Restricted Groups and select Add Group.

  4. Click Browse… and enter Greenbone Local Scan in the input box (see Fig. 6.16).

    _images/win_group_policy_check.png

    Fig. 6.16 Checking Microsoft Windows group names

  5. Click Check Names.

  6. Click OK twice to close the open windows.

  7. At This group is member of click Add.

  8. Enter Administrators in the input box Group (see Fig. 6.17) and click OK twice to close the open windows.

    Note

    On non-English systems enter the respective name of the local administrator group.

    _images/win_group_policy_member2.png

    Fig. 6.17 Adding a group membership

Configuring the Policy to Deny the Group Greenbone Local Scan Logging into the System Locally

  1. Click the policy Greenbone Local SecRights and select Edit.

  2. Select Computer Configuration > Policies > Windows Settings > Security Settings > Local Policies > User Rights Assignment in the left panel.

  3. In the right panel double click Deny log on locally.

  4. Activate the checkbox Define these policy settings and click Add User or Group.

  5. Click Browse… and enter Greenbone Local Scan in the input box (see Fig. 6.18).

  6. Click Check Names.

    _images/win_group_policy_deny.png

    Fig. 6.18 Editing the policy

  7. Click OK three times to close the open windows.

Configuring the Policy to Deny the Group Greenbone Local Scan Logging into the System Remotely

  1. Click the policy Greenbone Local SecRights and select Edit.

  2. Select Computer Configuration > Policies > Windows Settings > Security Settings > Local Policies > User Rights Assignment in the left panel.

  3. In the right panel double click Deny log on through Desktop Services.

  4. Activate the checkbox Define these policy settings and click Add User or Group.

  5. Click Browse… and enter Greenbone Local Scan in the input box (see Fig. 6.19).

  6. Click Check Names.

    _images/win_group_policy_deny2.png

    Fig. 6.19 Editing the policy

  7. Click OK three times to close the open windows.

Configuring the Policy to Give Read Permissions Only to the Registry for the Group Greenbone Local Scan

Important

This setting still exists after the GPO has been removed (“tattooing GPO”).

This changes fundamental privileges which may not be simply reversed by removing the GPO.

Research whether the settings are compatible with the environment.

Note

The following steps are optional.

  1. In the left panel right click Registry and select Add Key.

  2. Select USERS and click OK (see Fig. 6.20).

    _images/win_group_policy_reg.png

    Fig. 6.20 Selecting the registry key

  3. Click Advanced and Add.

  4. Enter Greenbone Local Scan in the input box and click OK (see Fig. 6.21).

    _images/win_group_policy_reg2.png

    Fig. 6.21 Selecting the group Greenbone Local Scan

  5. Select This object and child objects in the drop-down list Apply to.

  6. Deactivate all checkboxes for Allow and activate the checkboxes Set Value, Create Subkey, Create Link, Delete, Change Permissions and Take Ownership for Deny (see Fig. 6.22).

    _images/win_group_policy_reg3.png

    Fig. 6.22 Disallowing edition of the registry

  7. Click OK twice and confirm the warning message by clicking Yes.

  8. Click OK.

  9. Select the radio buttons Configure this key then and Propagate inheritable permissions to all subkeys and click OK (see Fig. 6.23).

    _images/win_group_policy_reg4.png

    Fig. 6.23 Making the permissions recursive

  10. Repeat the steps 2 to 9 for MACHINE and CLASSES_ROOT.

Linking the Group Policy Object

  1. In the right panel right click the domain and select Link an Existing GPO….

  2. Select Greenbone Local SecRights in the section Group Policy objects and click OK (see Fig. 6.24).

    _images/win_group_policy_link.png

    Fig. 6.24 Linking the policy

6.3.3.3. Restrictions

Based on the fact that write permissions to the registry and system drive have been removed, the following two tests will no longer work:

  • Leave information on scanned Windows hosts OID 1.3.6.1.4.1.25623.1.0.96171

    This test, if desired, creates information about the start and end of a scan under HKLM\Software\VulScanInfo. Due to denying write access to HKLM this is no longer possible. If the test should be possible, the GPO must be adjusted respectively.

  • Windows file Checksums OID 1.3.6.1.4.1.25623.1.0.96180

    This test, if desired, saves the tool ReHash under C:\Windows\system32 (for 32-bit systems) or C:\Windows\SysWOW64 (for 64-bit systems). Due to denying write access this is no longer possible. If the test should be possible, the tool must be saved separately or the GPO must be adjusted respectively.

6.3.3.4. Scanning Without Domain Administrator and Local Administrator Permissions

It is possible to build a GPO in which the user also does not have any local administrator permissions. But the effort to add respective read permissions to each registry branch and folder is huge. Unfortunately, inheriting of permissions is deactivated for many folders and branches. Additionally, these changes can be set by GPO but cannot be removed again (tattooing GPO). Specific permissions could be overwritten so that additional problems could occur as well.

Building a GPO in which the user does not have any local administrator permissions does not make sense from a technical and administrative point of view.

6.3.4. Requirements on Target Systems with Linux/Unix

  • For authenticated scans on Linux or Unix systems regular user access is usually enough. The login is performed via SSH. The authentication is done either with passwords or an SSH key stored on the GCS.

  • It needs to be made sure that public key authentication is not prohibited by the SSH daemon. The line PubkeyAuthentication no must not be present.

  • Existing SSH keys may also be used. SSH keys can be generated with OpenSSH by using the command ssh-keygen on Linux or puttygen.exe if using PuTTY on Microsoft Windows. The formats Ed25519 or RSA are recommended. All SSH keys must correspond to RFC 4716.

  • For scans that include policy testing, root permission or the membership in specific groups (often wheel) may be necessary. For security reasons many configuration files are only readable by super users or members of specific groups.

6.3.5. Requirements on Target Systems with ESXi

By default, local ESXi users are limited to read-only roles. Either an administrative account or a read-only role with permission to global settings has to be used. This can be set up as follows:

  1. Start the Vsphere client.

  2. Select Administration > Roles in the menu bar (see Fig. 6.25).

    _images/vsphere1.png

    Fig. 6.25 Vsphere client offering access to the roles

    → The roles are displayed.

  3. Right click ReadOnly and select Clone (see Fig. 6.26).

    _images/vsphere3.png

    Fig. 6.26 Displaying the roles

    → The cloned role is displayed as well.

  1. Right click the cloned role and select Rename.

  2. Enter the new name of the cloned role in the input box and click OK.

  3. Right click the cloned role and select Edit Role….

  4. Unfold Global and activate the checkbox Settings (see Fig. 6.27).

    _images/vsphere6.png

    Fig. 6.27 Editing the role

  5. Click OK.

  6. Select Inventory > Inventory in the menu bar.

  7. Open the tab Permissions.

  8. Right click in the empty space and select Add Permission… (see Fig. 6.28).

    _images/vsphere8.png

    Fig. 6.28 Adding a permission to the scan user

  9. Select the scan user account used by the GCS in the left section (see Fig. 6.29).

  10. Select the created role in the drop-down list in the right section (see Fig. 6.29).

  11. Click OK.

    _images/vsphere9.png

    Fig. 6.29 Assigning the role to the scan user

6.3.6. Requirements on Target Systems with Cisco OS

The GCS can check network components like routers and switches for vulnerabilities as well. While the usual network services are discovered and checked via the network, some vulnerabilities can only be discovered by an authenticated scan. For the authenticated scan the GCS can use SSH.

The GCS currently require only the command show version to retrieve the current version of the firmware of the device.

To set up a less privileged user which is only able to run this command, several approaches are possible. The following example uses the role based access control feature.

Tip

Before using the following example, make sure all side effects of the configuration are understood. If used without verification the system may restrict further logins via SSH or console.

To use role based access control AAA and views have to be enabled:

> enable
# configure terminal
(config)# aaa new-model
(config)# exit
> enable view
# configure terminal

The following commands create a restricted view including just the command show version. The supplied password view-pw is not critical:

(config)# parser view gcs-view
(config-view)# secret 0 view-pw
(config-view)# commands exec include show version
(config-view)# exit

Now the user gcs-user with the password gcs-pw is created and linked to the view gcs-view:

(config)# username gcs-user view gcs-view password 0 gcs-pw
(config)# aaa authorization console
(config)# aaa authorization exec default local

If SSH is not enabled yet the following commands take care of that. Use the appropriate host name and domain:

(config)# hostname switch
(config)# ip domain-name greenbone.net
(config)# crypto key generate rsa general-keys modulus 2048

Finally, enable SSH logins using the following commands:

(config)# line vty 0 4
(config-line)# transport input ssh
(config-line)# Crtl-Z

The credentials of the user need to be entered on the platform. Select Login Credentials (category Scan Configuration) in the menu panel and create the appropriate user (see Chapter 6.3.2).

Link the credentials to the target to be used as SSH credentials.

6.4. Performing a Scheduled Scan

For continuous vulnerability management the manual execution of task is tedious. The GCS support the scheduling of tasks for their automation and refer to schedules as automatic scans at a specific time. They can be run once or repeatedly.


gb_video The steps for creating and using schedules are briefly explained in a video.


6.4.1. Creating a Schedule

A new schedule can be created as follows:

  1. Select Schedules (category Scan Configuration) in the menu panel.

  2. Create a new schedule by clicking + Create New Schedule.

  3. Define the schedule (see Fig. 6.30).

_images/schedule_new.png

Fig. 6.30 Creating a new schedule

  1. Click Create Schedule.

    → The schedule is created and can be selected when creating a new task (see Chapter 6.2.4).

The following details of the schedule can be defined:

Schedule name

Definition of the name. The name can be chosen freely.

Description (optional)

An optional comment can contain additional information.

Start Time

Definition of the date and time for the first scan to start.

End Time

Definition of the date and time for the first scan to end.

By setting no end time, the scan runs indefinitely until it is finished.

Execution Interval

Definition of the repetition rate of the task. It can be selected between Daily, Weekly and Monthly. Additionally, the space between intervals is set.

Example: a scheduled task with an interval of Weekly and an interval spacing of 2 runs every two weeks.

6.4.2. Managing Schedules

All existing schedules can be displayed by selecting Schedules (category Scan Configuration) in the menu panel.

For all schedules the following information is displayed:

Name

Name of the schedule.

Comment

Optional description of the schedule.

Start Time

Start time of the first run of the task.

End Time

Optional end time of the first run of the task.

Interval Type

Time period between two runs of the task.

Interval Spacing

Space between intervals.

For all schedules the following actions are available:

  • edit Edit the schedule.

  • trashcan Delete the schedule. Only schedules which are currently not used can be deleted.

6.5. Managing Targets

All existing targets can be displayed by selecting Targets (category Scan Configuration) in the menu panel.

For all targets the following information is displayed:

Name

Name of the target.

Port List

Port list used if the target is used for a scan (see Chapter 6.2.4).

Verified

Status of the validation of the configured hosts.

IPs

Number of scanned hosts.

For all targets the following actions are available:

  • info Open an overlay with detailed information about the target.

  • edit Edit the target.

  • trashcan Delete the target. Only targets which are currently not used can be deleted.

  • assignment Show pending host validations (only for external targets).

Clicking info opens an overlay (see Fig. 6.31) containing the following information:

Target name

Name of the target.

Hosts

Hosts that are scanned if the target is used for a scan (see Chapter 6.2.4).

Port list

Port list used if the target is used for a scan (see Chapter 6.2.4).

Login Credentials

Credentials configured for the target.

_images/target_overlay.png

Fig. 6.31 Overlay containing information about the target

6.6. Managing Gateways

6.6.1. Page Gateways

All existing gateways can be displayed by selecting Gateways (category Scan Management) in the menu panel.

For all gateways the following information is displayed:

Location

Textual description of the location of the gateway.

Status

Status of the connection with the scanner.

Description

Optional description of the gateway.

For all gateways the following actions are available:

  • edit Edit the gateway.

  • trashcan Delete the gateway.

6.6.2. Gateway Administration Menu (CLI)

Note

The gateway can be imported to Microsoft Hyper-V or VMware ESXi.

Network settings of the gateway are managed using the gateway administration menu:

  1. Start the gateway in the virtual environment.

  2. After the boot process is completed, log in to the gateway administration menu. The default login information is:

    • User: admin

    • Password: admin

    → Actions for the gateway are displayed (see Fig. 6.32).

    _images/gateway_5.png

    Fig. 6.32 Managing a gateway

The following actions are available:

Network configuration

Set up the network of the gateway using DHCP or by entering IP address, netmask, DNS and gateway manually.

Test connections

Check whether all gateway connections work as intended.

Gateway configuration

Set the password for the gateway web interface and register the gateway.

Set cli password

Set the password for the gateway administration menu.

Setup SSL configuration

Set up a new SSL certificate.

Reboot

Reboot the gateway.

Logout

Log out from the gateway administration menu.

Shutdown

Shut down the gateway.

6.6.3. Gateway Web Interface

  1. Open the web browser and enter the following URL: https://<ip>. Replace <ip> with the IP address of the gateway.

    Tip

    The IP address can be displayed in the gateway administration menu by selecting Network configuration and pressing Enter (see Chapter 6.6.2).

  2. Log in using the user name admin and the password defined in the gateway administration menu (see Chapter 6.6.2).

  3. Select Overview in the menu panel to display the status and the ports of the gateway.

    _images/gateway_7.png

    Fig. 6.33 Gateway overview

  4. Select Settings in the menu panel.

    → The following actions are available:

    • Setting the API key of the gateway (see Chapter 6.2.3).

    • Setting the password for logging in to the gateway web interface.

    • Enabling/disabling error reporting.

6.7. Managing Tasks

All existing tasks can be displayed and managed on the pages Scan Management and Scan Configuration.

6.7.1. Page Scan Management


gb_video The scan management is briefly explained in a video.


Select Scan Management in the menu panel.

For all tasks the following information is displayed:

file

Open the latest report of the scan. For reading, managing and downloading reports see Chapter 7.

Task

Name of the task.

By clicking on the name of a task, an overlay with details is opened.

Status

Current status of the task. The following status bars are possible:

status_new The task has not been run since it was created.

status_exportreq The export of the task to the scan engine was requested.

status_exported The task was successfully exported to the scan engine.

status_exportfail The export of the task to the scan engine failed.

status_requested The task was just started. The GCS are preparing the scan.

status_running The scan is currently running. The column Progress provides further details.

status_deleted The task was deleted. The actual deletion process can take some time as reports need to be deleted as well.

status_stoprequested The task was requested to stop recently. However, the scan engine has not yet reacted to this request yet.

status_stopped The task was stopped. The latest report is possibly not yet complete. Other reasons for this status could be the reboot of the scan engine or a power outage. After restarting the scanner, the task will be resumed automatically.

status_done The task has been completed successfully.

status_error An error has occurred and the task was interrupted. The latest report is possibly not complete yet or is missing completely.

Progress

When the scan was started, further information about the scan status are displayed.

A percent value shows the completion of the scan based on the number of VTs executed on the selected hosts. For this reason the value does not necessarily correlate with the time spent.

Reports

Number of reports for the task. By clicking on the number, an overview of all reports is opened.

Last Scan

Date and time of the last scan of the task.

Target

Scan target that is examined when the task is run.

By clicking on the name of a target, an overlay with details is opened.

Executive PDF

By clicking download the “Executive Report” can be downloaded. It contains general information about the scan and lists of hosts sorted by severity.

Technical PDF

By clicking download the “Technical Report” can be downloaded. It contains general information about the scan as well as about the scanned hosts and details for each found vulnerability.

_images/scan_management.png

Fig. 6.34 Page Scan Management

6.7.2. Page Scan Configuration

Select Scan Configuration in the menu panel.

For all tasks the following information is displayed:

Name

Name of the task.

Type

Type of the target: internal or external.

Scan Target

Scan target that is examined when the task is run.

By clicking on the name of a target, an overlay providing details is opened.

Scan Configuration

Scan configuration that is used for the task.

Schedule

Schedule for this task (see Chapter 6.4).

By clicking on the name of a schedule, an overlay providing details is opened.

For all targets the following actions are available:

  • edit Edit the target.

  • trashcan Delete the target. Only targets which are currently not used can be deleted.

6.8. Scan Configurations

The GCS come with various predefined scan configurations.

The following configurations are available:

Discovery

This scan configuration only uses VTs that provide information about the target system. No vulnerabilities are being detected.

Amongst others, the collected information contains information about open ports, used hardware, firewalls, used services, installed software and certificates. The system is inventoried completely.

Host Discovery

This scan configuration is used to detect target systems. No vulnerabilities are being detected.

System Discovery

This scan configuration is used to detect target systems including installed operating systems and used hardware. No vulnerabilities are being detected.

Analysis [standard]

For many environments this is the best option to start with.

This scan configuration is based on the information gathered in the previous port scan and uses almost all VTs. Only VTs that will not damage the target system are used. VTs are optimized in the best possible way to keep the potential false negative rate especially low. The other configurations only provide more value in rare cases but with much higher effort.

Analysis [aggressive]

This scan configuration expands the scan configuration Analyze [Standard] with VTs that could disrupt services or systems or even cause shutdowns.

6.9. Port Lists

The port list configured for a target has a large impact on the duration of the alive test and the vulnerability scan of this target.

Ports are the connection points of network communication. Each port of a system connects with the port on another system.

Transmission Control Protocol (TCP) ports

  • 65535 TCP ports for each system

  • Data transmission occurs in both directions between two TCP ports.

  • The scan of TCP ports is usually performed simply and fast.

User Datagram Protocol (UDP) ports

  • 65535 UDP ports for each system

  • Data transmission occurs only in one directions between two UDP ports.

  • Data received by UDP are not necessarily confirmed, so the testing of UDP ports usually takes longer.

Ports 0 to 1023 are privileged or system ports and cannot be opened by user applications 2.

The Internet Assigned Numbers Authority (IANA) assigns ports to standard protocols, e.g., port 80 to “http” or port 443 to “https”. Over 5000 ports are registered.

Scanning all ports takes too long in many cases and many ports are usually not used. To overcome this, port lists can be used.

All ports of all systems of all internet accessible systems were analyzed and lists of the most used ports were created. Those do not necessarily reflect the IANA list because there is no obligation to register a specific service type for a respective port. Nmap, an open source port scanner, and the OpenVAS scanner use different lists by default and do not check all ports either.

For most scans it is often enough to scan the ports registered with the IANA.

The following port lists are predefined on the GCS:

  • All IANA assigned TCP 2012-02-10: all TCP ports assigned by IANA on 10th of February 2012

  • All privileged TCP

  • All privileged TCP and UDP

  • All TCP

  • OpenVAS Default: the TCP ports which are scanned by the OpenVAS scanner when passing the default port range preference

  • All IANA assigned TCP and UDP 2012-02-10: all TCP and UDP ports assigned by IANA on 10th of February 2012

  • All TCP and Nmap 5.51 top 100 UDP: all TCP ports and the top 100 UDP ports according to Nmap 5.51

  • All TCP and Nmap 5.51 top 1000 UDP: all TCP ports and the top 1000 UDP ports according to Nmap 5.51

  • Nmap 5.51 top 2000 TCP and top 100 UDP: the top 2000 TCP ports and the top 100 UDP ports according to Nmap 5.51

  • Web services

6.10. Using Notifications

The user can receive summaries about the configured scans and alerts for completed scans (see Chapter 5.4).

6.11. Obstacles While Scanning

There are several typical problems which might occur during a scan using the default values of the GCS. While the default values of the GCS are valid for most environments and customers, depending on the actual environment and the configuration of the scanned hosts they might require some tweaking.

6.11.1. Hosts not Found

During a typical scan (either Discovery or Analysis [Standard]) the scanner will first use the ping command to check the availability of the configured targets by default. If the target does not reply to the ping request it is presumed to be dead and will not be scanned by the port scanner or any VT.

In most LAN environments this does not pose any problems because all devices will respond to a ping request. But sometimes (local) firewalls or other configuration might suppress the ping response. If this happens, the target will not be scanned and will not be included in the results and the scan report.

To remediate this problem, both the target configuration and the scan configuration support the setting of the alive test (see Alive Test).

If the target does not respond to a ping request, a TCP ping may be tested.

6.11.2. Long Scan Periods

Once the target is discovered to be alive using the ping command, the scanner uses a port scanner to scan the target. By default, a TCP port list containing around 5000 ports is used. If the target is protected by a (local) firewall dropping most of these packets the port scan will need to wait for the timeout of each individual port. If the hosts are protected by (local) firewalls the port lists or the firewalls may be tuned. If the firewall does not drop the request but rejects the request the port scanner does not have to wait for the timeout. This is especially true if UDP ports are included in the scan.

Footnotes

1

The maximum netmask is /20. This equals 4096 addresses.

2

On Unix-like systems, access to privileged ports is restricted to privileged users (i.e., root). Ports starting at 1024 are also available to non-privileged users.