FreeBSD 4.5 syncache / syncookies Denial Of Service Vulnerability
FreeBSD suggests that one of these issues may be dealt with by disabling syncookies through the following command:
# sysctl -w net.inet.tcp.syncookies=0
This issue was resolved in 4.5-STABLE on January 21, 2002.
A patch is also available. The following patch instructions have been supplied:
Execute the following commands as root:
# cd /usr/src
# patch -p < /path/to/patch
Recompile your kernel as described in http://www.freebsd.org/handbook/kernelconfig.html and reboot the system.
FreeBSD FreeBSD 4.5 -RELEASE
FreeBSD FreeBSD 4.5 -STABLE