The strange decline of computer worms
Although windows-centric, theregister has published an article on the lessening numbers of "Slammer-style worms". They attribute this decline to "the widespread use of XP SP2 and greater use of personal firewall" rendering "worms far less potent in the same way that boot sector viruses died out with Windows 95 and the introduction of Office 2000 made macro viruses far less common."
"Whilst standard computer worms have experienced a relative decline, email worms have remained a problem and instant message security threats are becoming a greater concern. "A worm that exploited an IM vulnerability to spread could spread very quickly and travel straight through firewalls," Mikko Hyppönen, director of anti-virus research at F-Secure, warned. Spyware, Trojans and other types of software that turn PCs into zombie drones in botnets, and the increased sophistication of viruses capable of infecting mobile phones also remain key security concerns."