OL6-00-000095 - The system must be configured to use TCP syncookies when experiencing a TCP SYN flood.

Information

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.

Solution

To set the runtime status of the 'net.ipv4.tcp_syncookies' kernel parameter, run the following command:

# sysctl -w net.ipv4.tcp_syncookies=1

If this is not the system's default value, add the following line to '/etc/sysctl.conf':

net.ipv4.tcp_syncookies = 1

See Also

https://dl.dod.cyber.mil/wp-content/uploads/stigs/zip/U_Oracle_Linux_6_V2R7_STIG.zip

Item Details

Category: SYSTEM AND COMMUNICATIONS PROTECTION

References: 800-53|SC-5(2), CAT|II, CCI|CCI-001095, Rule-ID|SV-208862r793647_rule, STIG-ID|OL6-00-000095, STIG-Legacy|SV-64889, STIG-Legacy|V-50683, Vuln-ID|V-208862

Plugin: Unix

Control ID: 6fd1283c15b946556081ed144d9487ffe491910a1230a3722ea94bd7e500f029