SuSEfirewall2 must protect against or limit the effects of Denial-of-Service (DoS) attacks on the SUSE operating system by implementing rate-limiting measures on impacted network interfaces.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-77437	SLES-12-030040	SV-92133r3_rule		High

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. This requirement addresses the configuration of the SUSE operating system to mitigate the impact on system availability of DoS attacks that have occurred or are ongoing. For each system, known and potential DoS attacks must be identified and solutions for each type implemented. A variety of technologies exist to limit or, in some cases, eliminate the effects of DoS attacks (e.g., limiting processes or establishing memory partitions). Employing increased capacity and bandwidth, combined with service redundancy, may reduce the susceptibility to some DoS attacks.

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. This requirement addresses the configuration of the SUSE operating system to mitigate the impact on system availability of DoS attacks that have occurred or are ongoing. For each system, known and potential DoS attacks must be identified and solutions for each type implemented. A variety of technologies exist to limit or, in some cases, eliminate the effects of DoS attacks (e.g., limiting processes or establishing memory partitions). Employing increased capacity and bandwidth, combined with service redundancy, may reduce the susceptibility to some DoS attacks.

STIG	Date
SLES 12 Security Technical Implementation Guide	2018-09-27

Details

Check Text ( C-76993r2_chk )
Verify "SuSEfirewall2" is configured to protect the SUSE operating system against or limit the effects of DoS attacks. Run the following command: # grep -i fw_services_accept_ext /etc/sysconfig/SuSEfirewall2 FW_SERVICES_ACCEPT_EXT="0/0,tcp,22,,hitcount=3,blockseconds=60,recentname=ssh" If the "FW_SERVICES_ACCEPT_EXT" rule does not contain both the "hitcount" and "blockseconds" parameters, this is a finding.

Check Text ( C-76993r2_chk )

Verify "SuSEfirewall2" is configured to protect the SUSE operating system against or limit the effects of DoS attacks.

Run the following command:

# grep -i fw_services_accept_ext /etc/sysconfig/SuSEfirewall2
FW_SERVICES_ACCEPT_EXT="0/0,tcp,22,,hitcount=3,blockseconds=60,recentname=ssh"

If the "FW_SERVICES_ACCEPT_EXT" rule does not contain both the "hitcount" and "blockseconds" parameters, this is a finding.

Fix Text (F-84077r2_fix)
Configure "SuSEfirewall2" to protect the SUSE operating system against or limit the effects of DoS attacks by implementing rate-limiting measures on impacted network interfaces. Add or replace the following line in "/etc/sysconfig/SuSEfirewall2": FW_SERVICES_ACCEPT_EXT="0/0,tcp,22,,hitcount=3,blockseconds=60,recentname=ssh" The firewall must be restarted in order for the changes to take effect. # sudo systemctl restart SuSEfirewall2.service

Fix Text (F-84077r2_fix)

Configure "SuSEfirewall2" to protect the SUSE operating system against or limit the effects of DoS attacks by implementing rate-limiting measures on impacted network interfaces.

Add or replace the following line in "/etc/sysconfig/SuSEfirewall2":

FW_SERVICES_ACCEPT_EXT="0/0,tcp,22,,hitcount=3,blockseconds=60,recentname=ssh"

The firewall must be restarted in order for the changes to take effect.

# sudo systemctl restart SuSEfirewall2.service