The threat is real, so a field of study has been born out of the need to be one-step ahead of the writers of malware
. Cryptovirology, the discipline itself, focuses on the use of encryption software and key generation in relation to the production of malware. Knowing what a computer worm is would give you a hint as to how dangerous this type of program is; make sure your system is amply protected. Otherwise, you might wake up one day looking at a warped system.