'Crackers' are small programs that patch specific software they are written for to disable copy protection or/and to unlock some locked features. These are usually standalone programs that do not do any harm to computer system. Being run they search for specific file (usually with hardcoded name) and change some bytes in it. Most of crackers are packed with home-made encryption/protection routines.
Depending on the settings of your F-Secure security product, it will either automatically delete, quarantine or rename the suspect file, or ask you for a desired action.
More information on the scanning and removal options available in your F-Secure product can be found in the Help Center.
You may also refer to the Knowledge Base on the F-Secure Community site for more information.