The F5 BIG-IP DNS server implementation must manage excess capacity, bandwidth, or other redundancy to limit the effects of information flooding types of denial-of-service (DoS) attacks.

Severity	Group ID	Group Title	Version	Rule ID	Date	STIG Version
medium	V-265991	SRG-APP-000247-DNS-000036	F5BI-DN-300039	SV-265991r1024501_rule	2024-09-09	1

Description
DoS is a condition when a resource is not available for legitimate users. When this occurs, the organization either cannot accomplish its mission or must operate at degraded capacity. In the case of application DoS attacks, care must be taken when designing the application to ensure the application makes the best use of system resources. SQL queries have the potential to consume large amounts of CPU cycles if they are not tuned for optimal performance. Web services containing complex calculations requiring large amounts of time to complete can bog down if too many requests for the service are encountered within a short period of time. A DoS attack against the DNS infrastructure has the potential to cause a DoS to all network users. As the DNS is a distributed backbone service of the internet, various forms of amplification attacks resulting in DoS, while using the DNS, are still prevalent on the internet today. Some potential DoS flooding attacks against the DNS include malformed packet flood, spoofed source addresses, and distributed DoS. Without the DNS, users and systems would not have the ability to perform simple name-to-IP resolution. Configuring the DNS implementation to defend against cache poisoning, employing increased capacity and bandwidth, building redundancy into the DNS architecture, using DNSSEC, limiting and securing recursive services, DNS black holes, etc., may reduce the susceptibility to some flooding types of DoS attacks. Satisfies: SRG-APP-000247-DNS-000036, SRG-APP-000246-DNS-000035

Description

DoS is a condition when a resource is not available for legitimate users. When this occurs, the organization either cannot accomplish its mission or must operate at degraded capacity. In the case of application DoS attacks, care must be taken when designing the application to ensure the application makes the best use of system resources. SQL queries have the potential to consume large amounts of CPU cycles if they are not tuned for optimal performance. Web services containing complex calculations requiring large amounts of time to complete can bog down if too many requests for the service are encountered within a short period of time. A DoS attack against the DNS infrastructure has the potential to cause a DoS to all network users. As the DNS is a distributed backbone service of the internet, various forms of amplification attacks resulting in DoS, while using the DNS, are still prevalent on the internet today. Some potential DoS flooding attacks against the DNS include malformed packet flood, spoofed source addresses, and distributed DoS. Without the DNS, users and systems would not have the ability to perform simple name-to-IP resolution. Configuring the DNS implementation to defend against cache poisoning, employing increased capacity and bandwidth, building redundancy into the DNS architecture, using DNSSEC, limiting and securing recursive services, DNS black holes, etc., may reduce the susceptibility to some flooding types of DoS attacks. Satisfies: SRG-APP-000247-DNS-000036, SRG-APP-000246-DNS-000035

ℹ️ Check
From the BIG-IP GUI: 1. Security. 2. DoS Protection. 3. Device Protection. 4. Expand DNS and verify the "State" is set to "Mitigate" for all signatures. If the BIG-IP appliance is not configured to restrict the ability of individuals to use the DNS server to launch DoS attacks against other information systems, this is a finding.

✔️ Fix
This requires the AFM license or can be implemented using another firewall's ACL. From the BIG-IP GUI: 1. Security. 2. DoS Protection. 3. Device Protection. 4. Expand DNS and do the following for each: a. Check the box at the top of the list of signatures to select all. b. Set "Set State" to "Mitigate". c. Click "Commit Changes to System". Note: Sites must operationally test, adjust thresholds, or initially use learning mode prior to turning on mitigation to prevent operational impacts, particularly in implementations with large traffic volumes.

✔️ Fix

This requires the AFM license or can be implemented using another firewall's ACL. From the BIG-IP GUI: 1. Security. 2. DoS Protection. 3. Device Protection. 4. Expand DNS and do the following for each: a. Check the box at the top of the list of signatures to select all. b. Set "Set State" to "Mitigate". c. Click "Commit Changes to System". Note: Sites must operationally test, adjust thresholds, or initially use learning mode prior to turning on mitigation to prevent operational impacts, particularly in implementations with large traffic volumes.