I receive the error "Your connection to this secure server has been rejected. Because of past cheating violations, you have been banned from playing on all secure servers." when attempting to join a server - what does it mean?
This message indicates that your account has been banned by the Valve Anti-Cheat (VAC) system for cheating. There are several important considerations for VAC-banned accounts:
STEAM SUPPORT CANNOT REMOVE THE BAN ON YOUR ACCOUNT
Regardless of who was using your account at the time it was banned, the use and security of your Steam account is your responsibility.
THE DETAILS OF THE BAN WILL NOT BE PROVIDED
Steam Support will not disclose the cheats that were detected running on your system or the date and time the infraction took place. Any requests for this information will be ignored.
VAC may not ban you immediately - the cheating violation may have occurred days or even weeks before the ban is apparent on your account.
YOUR ACCOUNT MAY STILL BE USED TO PLAY SINGLE-PLAYER GAMES AND MULTIPLAYER GAMES ON UNSECURED SERVERS
Your account may still be used to play single-player games or to connect to non-secure game servers and for games played over a LAN. To find non-secure servers, please change your filter settings in the server browser list to show servers which are not VAC-secured (from the Steam main menu go to the View option, select Servers and then select "Not secure" in the Anti-Cheat drop-down).
YOU CAN NOT TRANSFER YOUR GAMES TO A DIFFERENT ACCOUNT
Steam Support will not release your CD Key(s) to be used on other accounts. Do not register retail products or purchase new Steam subscriptions on a VAC banned account.
If you choose to purchase a new copy of the game, please register it or install it under a newly-created Steam account. Prior to installing, remove all cheats from your system - if you do not know how or where the cheats were installed, you may want to consider reformatting your hard drive(s) and starting over with a fresh installation of your operating system.