Valve's Eric Smith has sent word along the HLDS mailing list that the Valve has updated server security modules again.
Security module update
*** This only affects Counter-Strike servers. ***
We've updated the public security modules again. Your Counter-Strike servers should update themselves automatically. If you find your servers are suddenly having problems, try restarting the servers.
These modules should detect OGC's OpenGl Hack 1.8 and will start reporting detected cheaters to our master ban list server. We won't be banning anyone yet, but we'll be gathering information about detected cheaters. You will see outgoing traffic to: 22.214.171.124:27013.