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The system must be configured to use TCP syncookies when experiencing a TCP SYN flood.


Overview

Finding ID Version Rule ID IA Controls Severity
V-22419 GEN003612 SV-46277r1_rule Medium
Description
A TCP SYN flood attack can cause Denial of Service by filling a system's TCP connection table with connections in the SYN_RCVD state. Syncookies are a mechanism used to only track a connection when a subsequent ACK is received, verifying the initiator is attempting a valid connection and is not a flood source. This technique does not operate in a fully standards-compliant manner, but is only activated when a flood condition is detected, and allows defense of the system while continuing to service valid requests.
STIG Date
SUSE Linux Enterprise Server v11 for System z 2016-12-20

Details

Check Text ( C-36832r1_chk )
Verify the system configured to use TCP syncookies when experiencing a TCP SYN flood.
# cat /proc/sys/net/ipv4/tcp_syncookies
If the result is not "1", this is a finding.
Fix Text (F-31670r1_fix)
Configure the system to use TCP syncookies when experiencing a TCP SYN flood.
Edit /etc/sysctl.conf and add a setting for "net.ipv4.tcp_syncookies=1".
# sysctl -p