The Rogue Spear Retreat has posted an interview with Red Storm Entertainment's Greg Stelmack, talking about the measures being taken to prevent cheating in Rogue Spear, the sequel to Rainbow Six. Here's an excerpt:

"Game developers walk a fine line between letting people tweak the game and preventing cheating. The constants file caused a lot of cheating issues, so we've completely removed it for Rogue Spear. All those constants are now rolled into the executable. We've caught lots of other configuration files and made sure that the server sends them across so that everyone has the same values. I'm sure there are still some server side cheats (e.g. the server customizing one particular gun), but if you can't trust your server in a multiplayer game, you can't trust anyone. We can't eliminate those without preventing people from editing weapons or making other mods."