Every month, critical vulnerabilities are reported on a wide variety of operating systems and applications. Computer virus attacks are quickly becoming the number one security problem which ranges between large scale social engineering attacks and exploiting critical vulnerabilities. Sophisticated attacks use polymorphism and even metamorphism mixed with cryptographically strong algorithms and self-updating which makes analysis and defense increasingly difficult. This presentation will discuss the state of the art in computer viruses and computer virus defense. I will present some promising host-based prevention techniques that can stop entire classes of fast-spreading worms such W32/Sobig@mm and W32/Mydoom@mm as well as worms using buffer overflow attacks, such as Win32/CodeRed, Linux/Slapper, Win32/Slammer and Win32/Blaster. In-depth worm and exploit analysis are also discussed. It is becoming increasingly important to find ways to bridge the gap between computer virus research and general security research. The primary goal of this presentation is to encourage the fight against computer viruses within the security community.