Putting this here too:
There are currently at least four malicious servers (the IPs and names are irrelevant and can change randomly). If your auth is suddenly refusing to work and/or you see “Unknown” in the server list instead of “FREEZE”, you probably have connected to one of those servers and downloaded at least one map. All those maps contain malicious code. If you think you may be affected, delete all maps downloaded on September 14 or later and change your auth key. Downloading any maps from servers you don’t know well is discouraged until further notice.