Quote Originally Posted by Lifepower
Quote Originally Posted by BytePtr
Do not display messageboxes like: Game cheating program is active, Please close it before running game".
Just curious. Is there any game doing that?
Yes. Spyro the Dragon on PSX. It had CRCs of sections of code embedded in the section of code that it was doing the CRC on. These CRC'd sections of code would also overlap with other CRC'd sections of code. When it detected that a CRC did not match, it did not inform the user straight away. It removed a few gems from the level so the user could not complete the level, or later on a NPC character would mention that you are using a cracked version of the game. That was just one of the anti-crack methods they used. It took the crackers over three months to release a properly cracked version of Spyro with several dud versions released beforehand (the majority of a game's sales are in the first three months), and the crackers thanked the Spyro developers for making it such a challenge.

Here's the article on Gamasutra.
Keeping the Pirates at Bay: Implementing Crack Protection for Spyro: Year of the Dragon