The Photon operating system must use Transmission Control Protocol (TCP) syncookies.

Severity	Group ID	Group Title	Version	Rule ID	Date	STIG Version
medium	V-256512	SRG-OS-000142-GPOS-00071	PHTN-30-000036	SV-256512r958528_rule	2024-12-16	1

Description
A TCP SYN flood attack can cause a denial of service by filling a system's TCP connection table with connections in the SYN_RCVD state. Syncookies can be used to track a connection when a subsequent ACK is received, verifying the initiator is attempting a valid connection and is not a flood source. This feature is activated when a flood condition is detected and enables the system to continue servicing valid connection requests. Satisfies: SRG-OS-000142-GPOS-00071, SRG-OS-000420-GPOS-00186

Description

A TCP SYN flood attack can cause a denial of service by filling a system's TCP connection table with connections in the SYN_RCVD state. Syncookies can be used to track a connection when a subsequent ACK is received, verifying the initiator is attempting a valid connection and is not a flood source. This feature is activated when a flood condition is detected and enables the system to continue servicing valid connection requests. Satisfies: SRG-OS-000142-GPOS-00071, SRG-OS-000420-GPOS-00186

ℹ️ Check
At the command line, run the following command: # /sbin/sysctl -a --pattern tcp_syncookies Expected result: net.ipv4.tcp_syncookies = 1 If the output does not match the expected result, this is a finding.

✔️ Fix
At the command line, run the following commands: # sed -i -e "/^net.ipv4.tcp_syncookies/d" /etc/sysctl.conf # echo net.ipv4.tcp_syncookies=1>>/etc/sysctl.conf # /sbin/sysctl --load