SECURITY SET NOSPOOF

Usage: SECURITY SET NOSPOOF [on|off]

This turns on or off IP address spoof protection. This will prevent spoofed IP addresses from getting on the server. Most current operating systems like Windows2000, FreeBSD, Solaris7+ and Linux do not need this feature enabled.

Example:
/as security set nospoof on
/as security set nospoof off

If you do not have a reason to turn this off, leave it on. Nospoof protection is important to make bans work and to identify users.