100% secure against cheaters? Never. At the very least script kiddies and hackors get a hold of your IP address and crash everything. As for the game itself some cheats are so insidious and varied that nothing less than a check of all game files followed by total lockout of all game files on the client end would do the trick. But this is too difficult to impliment. Instead sysadmins continue to fight the good fight with some tools but mostly with some type of server police.

Depends on the cheat (mods on a server banning all client mods is a cheat) itself. While I am not going to give away all of the sysadmin details here, I will say some things. An increase in server load (may cause in-game lag) for the amount of players playing plus errors and warnings cropping up in the flserver console window are some things to look for server side. Obvious things in the game to see is the mod in action, also timing palyers going from one system to another. For example I knew it took about 1.5 mins to traverse Cali system from Cortez to NY. One guy did it in 30 secs and then I caught him doing 1200 thrusting IN the trade lane. Some people never learn.

Use FLSO to ban someone that has been kicked by flserver. Enable more and better kicking for flserver by installing the v1.1 patch (it's ONLY for flserver installs, not for FL clients!) and install Lancerguard (modifies INI files making it a kicking effect to have certain equipment NOT in MP on a ship).

Sounds like a server side mod. Some are stand alone, in other words the clients do not need to install or change their default install of FL. Some require a mod to be installed, which is handled by FLMM. If you have played SP and remember it, anything that was done by the game AI there can be mostly resurrected through a mod.

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Earendil
SysAdmin of Boston Freelancer server
See server rules and server news for more info.