Because trading in pirated software is illegal, these Web sites keep changing hosts and URLs as many as three times a month. However, as soon as one warez site moves or closes down, messages pointing to new locations start appearing almost immediately on Usenet groups. Businesses and universities inadvertently become hosts for warez. A cracker will find and exploit weaknesses in the server to host his site and will then create folders buried deep within the server and copy warez into those servers. A clever programmer using commonly available tools like Hex Editors and Disassemblers can break time limited or demo versions of software.
Cracks are much easier to find than warez sites.
There are at least 23 crack search engines on the Net and most of these claim to be updated daily. But their use is definitely illegal. A keygen works by using the same mathematical algorithm that the software manufacturer uses to generate a serial number. It is based on the letters of your name. But there's very little these companies can do except for alerting the authorities.