Crypto: Not Just for the Defensive Team

Cryptography has long been a useful, important tool for defensive computer security. Increasingly, however, attackers are using cryptographic techniques for the same reason as the defenders: to protect code's confidentiality and integrity. But in this case, the code is malicious. This paper reviews uses of encryption by writers of malicious code, through some recent examples. Malicious-code writers are using state-of-the-art cryptography, just as commercial security engineers are.