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Manual Chapter: Detecting and preventing SIP DoS Attacks on a Virtual Server
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About detecting and preventing SIP DoS attacks on a virtual server

Session Initiation Protocol (SIP) is a signaling protocol that is typically used to control communication sessions, such as voice and video calls over IP.

SIP DoS attack detection and prevention serves several functions:

  • To detect and report on SIP packets based on behavior characteristics of the sender or characteristics of the packets, without enforcing any rate limits.
  • To detect, report on, and rate limit SIP packets based on behavior characteristics that signify specific known attack vectors.
  • To identify Bad Actor IP addresses from which attacks appear to originate, by detecting packets per second from a source, and to apply rate limits to such IP addresses.
  • To blacklist Bad Actor IP addresses, with configurable detection times, blacklist durations, and blacklist categories, and allow such IP addresses to be advertised to edge routers to offload blacklisting.

You can use a SIP DoS profile to specify the percentage increase over the system baseline, which indicates that a possible attack is in process on a particular SIP method, or an increase in anomalous packets. You can also rate limit packets of known vectors. For all SIP vectors except sip-malformed, the system can manage thresholds automatically or manually. You can manually set thresholds for malformed SIP packets.

You can specify an address list as a whitelist, that the DoS checks allow. Whitelisted addresses are not subject to the checks configured in the DoS profile.

To protect a virtual server from SIP DoS attacks, you need to associate the virtual server with a DoS profile that includes SIP security.

Important: You must also create a SIP profile, and attach it to the virtual server being protected from SIP DoS attacks.

Task list

Detecting and preventing SIP DoS attacks with a DoS profile

This task describes how to create a new DoS profile and configure SIP settings to identify SIP attacks at the same time. However, you can also add SIP attack detection settings to an existing DoS profile. The BIG-IP® system handles SIP attacks that include malformed packets, protocol errors, and malicious attack vectors. Protocol error attack detection recognizes malformed and malicious packets, or packets that are employed to flood the system with several different types of responses.
  1. On the Main tab, click Security > DoS Protection > DoS Profiles .
    The DoS Profiles list screen opens.
  2. Click Create.
    The New DoS Profile screen opens.
  3. In the Name field, type the name for the profile.
  4. Click Finished.
    The DoS Protection: DoS Profiles screen opens.
  5. Click the name of the DoS profile you want to modify.
  6. Select the Threshold Sensitivity.
    Select Low, Medium, or High. A lower setting means the automatic threshold algorithm is less sensitive to changes in traffic and CPU usage, but will also trigger fewer false positives.
  7. If you have created a whitelist on the system, in the Default Whitelist field, begin typing the name of the address list to use as the whitelist, and select the list when the name appears.
  8. To define an address list to use as a whitelist, on the right side of the screen in the Shared Objects pane, click the + next to Address Lists.
    The Address List Properties pane opens.
  9. To configure SIP security settings, on the menu bar, select Protocol Security, and choose SIP Security.
  10. To change the threshold or rate increase for a particular SIP vector, in the Attack Type column, click the vector name.
    The vector properties pane opens on the right.
  11. From the State list, choose the appropriate enforcement option.
    • Select Mitigate to enforce the configured DoS vector by examining packets, logging the results of the vector, learning patterns, alerting to trouble, and mitigating the attack (watch, learn, alert, and mitigate).
    • Select Detect Only to configure the vector, log the results of the vector without applying rate limits or other actions, and alerting to trouble (watch, learn, and alert).
    • Select Learn Only to configure the vector, log the results of the vector, without applying rate limits or other actions (watch and learn).
    • Select Disabled to disable logging and enforcement of the DoS vector (no stat collection, no mitigation).
  12. For Threshold Mode, select whether to have the system determine thresholds for the vector (Fully Automatic), have partially automatic settings (Manual Detection / Auto Mitigation), or, you can control the settings (Fully Manual).
    The settings differ depending on the option you select. Here, we describe the settings for automatic threshold configuration. If you want to set thresholds manually, select one of the manual options and refer to online Help for details on the settings.
  13. To allow the DoS vector thresholds to be automatically adjusted, for Threshold Mode, select Fully Automatic.
    1. In the Attack Floor EPS field, type the number of events per second of the vector type to allow at a minimum, before automatically calculated thresholds are determined.
      Because automatic thresholds take time to be reliably established, this setting defines the minimum packets allowed before automatic thresholds are calculated.
    2. In the Attack Ceiling EPS field, specify the absolute maximum allowable for packets of this type before automatically calculated thresholds are determined.
      Because automatic thresholds take time to be reliably established, this setting rate limits packets to the events per second setting, when specified. To set no hard limit, set this to Infinite.
  14. To detect IP address sources from which possible attacks originate, enable Bad Actor Detection.
    Note: Bad Actor Detection is not available for every vector.
  15. To automatically blacklist bad actor IP addresses, select Add Source Address to Category.
    Important: For this to work, you need to assign an IP Intelligence policy to the appropriate context (device, virtual server, or route domain). For the device, assign a global policy: Security > Network Firewall > IP Intelligence > Policies . For the virtual server or route domain, assign the IP Intelligence policy on the Security tab.
  16. From the Category Name list, select the blacklist category to which to add blacklist entries generated by Bad Actor Detection.
  17. In the Sustained Attack Detection Time field, specify the duration in seconds after which the attacking endpoint is blacklisted. By default, the configuration adds an IP address to the blacklist after one minute (60 seconds).
  18. In the Category Duration Time field, specify the length of time in seconds that the address will remain on the blacklist. The default is 14400 seconds (4 hours).
  19. To allow IP source blacklist entries to be advertised to edge routers so they will null route their traffic, select Allow External Advertisement.
    Note: To advertise to edge routers, you must configure a Blacklist Publisher and Publisher Profile at Security > Options > External Redirection > Blacklist Publisher .
  20. Click Update to save your changes.
You have now configured a DoS profile to provide custom responses to malformed SIP attacks, SIP flood attacks, and to allow such attacks to be identified in system logs and reports.
Now you need to associate the DoS profile with a virtual server to apply the settings in the profile to traffic on that virtual server. When a SIP attack on a specific query type is detected, you can be alerted with various system monitors.

Creating a SIP profile for SIP DoS protection

You can create a SIP profile if configuring SIP DoS protection.
  1. On the Main tab, click Local Traffic > Profiles > Services > SIP (legacy) .
    The SIP profile list screen opens.
  2. Click Create.
    The New SIP Profile screen opens.
  3. In the Name field, type a unique name for the profile.
  4. Next to Settings, select the Custom check box.
  5. Select the SIP Firewall check box.
    When enabled, the SIP Security settings configured in the DoS Profile apply to the virtual servers that use this profile.
  6. Next to Log Settings, select the Custom check box.
  7. From the Log Publisher list, select a destination to which the BIG-IP system sends log entries.
    You can specify publishers for other DoS types in the same profile, for example, for DNS, Network, or Application DoS Protection.
  8. In the Log Settings area, from the Logging Profile list, select a custom Logging profile.
  9. Modify other settings, as required.
  10. Click Update.
A SIP profile is now configured for SIP DoS firewall features.
Assign this SIP profile to a virtual server, along with a DoS profile that includes SIP security, to provide SIP protocol DoS protection on a virtual server.

Assigning a SIP profile to a virtual server

You need to have created a SIP profile already.
To apply the settings in the SIP profile to traffic, you associate the SIP profile with a virtual server.
  1. On the Main tab, click Local Traffic > Virtual Servers .
    The Virtual Server List screen opens.
  2. Click the name of the virtual server you want to modify.
  3. From the Configuration list, select Advanced.
  4. From the SIP Profile list, select the name of the SIP profile that you previously created.
  5. Click Update.
The virtual server now uses the SIP settings from the SIP profile.

Associating a DoS profile with a virtual server

You must first create a DoS profile separately, to configure denial-of-service protection for applications, the DNS protocol, or the SIP protocol. For application-level DoS protection, the virtual server requires an HTTP profile (such as the default http).
You add denial-of-service protection to a virtual server to provide enhanced protection from DoS attacks, and track anomalous activity on the BIG-IP® system.
  1. On the Main tab, click Local Traffic > Virtual Servers .
    The Virtual Server List screen opens.
  2. Click the name of the virtual server you want to modify.
  3. On the menu bar, from the Security menu, choose Policies.
  4. To enable denial-of-service protection, from the DoS Protection Profile list, select Enabled, and then, from the Profile list, select the DoS profile to associate with the virtual server.
  5. Click Update to save the changes.
DoS protection is now enabled, and the DoS Protection profile is associated with the virtual server.

Allowing addresses to bypass DoS profile checks

You can specify whitelisted addresses that the DoS Profile does not subject to DoS checks. Whitelist entries are specified on a security address list, and can be configured directly on the DoS Profile screen.
  1. On the Main tab, click Security > DoS Protection > DoS Profiles .
    The DoS Profiles list screen opens.
  2. Click the name of the DoS profile you want to modify.
  3. If you have created a whitelist on the system, in the Default Whitelist field, begin typing the name of the address list to use as the whitelist, and select the list when the name appears.
  4. To define an address list to use as a whitelist, on the right side of the screen in the Shared Objects pane, click the + next to Address Lists.
    The Address List Properties pane opens.
  5. Type a Name for the address list.
  6. In the Contents field, type an address, and click Add. Repeat this step to add all items you want on the whitelist.
    You can type an IP address, a geographic location, or the name of another address list. Begin typing, and select the object when the name appears.
  7. Click Update to create the address list.
    If this is a new address list, type and select the address list name in the Default Whitelist field.
  8. Click Update to update the DoS Profile.
You have now configured a whitelist of addresses to bypass DoS checks for a DoS profile.

Creating a custom SIP DoS Protection Logging profile

Create a custom Logging profile to log SIP DoS Protection events and send the log messages to a specific location.
  1. On the Main tab, click Security > Event Logs > Logging Profiles .
    The Logging Profiles list screen opens.
  2. Click Create.
    The Create New Logging Profile screen opens.
  3. In the Logging Profile Properties, select the DoS Protection check box.
    The DoS Protection tab opens.
  4. In the SIP DoS Protection area, from the Publisher list, select the publisher that the BIG-IP system uses to log SIP DoS events.
    You can specify publishers for other DoS types in the same profile, for example, for DNS or Application DoS Protection.
  5. Click Finished.
Assign this custom SIP DoS Protection Logging profile to a virtual server.

Logging DoS events on a virtual server

Ensure that at least one log publisher exists on the BIG-IP® system.
Assign a custom logging profile to a virtual server when you want the system to log DoS protection events for the traffic the virtual server processes.
  1. On the Main tab, click Local Traffic > Virtual Servers .
    The Virtual Server List screen opens.
  2. Click the name of the virtual server you want to modify.
  3. On the menu bar, click Security > Policies .
    The screen displays policy settings for the virtual server.
  4. In the Log Profile setting, select Enabled. Then, select one or more profiles, and move them from the Available list to the Selected list.
  5. Click Update to save the changes.
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