UCF STIG Viewer Logo

The Photon operating system must use TCP syncookies.


Finding ID Version Rule ID IA Controls Severity
V-239109 PHTN-67-000037 SV-239109r816622_rule Medium
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
VMware vSphere 6.7 Photon OS Security Technical Implementation Guide 2022-06-17


Check Text ( C-42320r816620_chk )
At the command line, execute 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 Text (F-42279r816621_fix)
Open /etc/sysctl.conf with a text editor.

Add or update the following line:


Run the following command to load the new setting:

# /sbin/sysctl --load