Among other things, this article covers the human engineering factors in virus writing, the state-of-the-art in combating viruses by antivirus software companies, and the real scenarios we are likely to see in the future. The article is very infomative, and includes input from a several different virus writers.
On a related note, The Wilcox Family Says Goodbye to Internet Explorer: Mozilla has become our default browser for the time being, as I am waiting for some very scary Browser Helper Object vulnerabilities (and other exploits) to be repaired in IE. I’ve had one virus make it past Norton Antivirus in the form of a BHO (it was caught in my nightly scan, and did no damage), and my team leader, who is tech-saavy enough to write his own viruses and extremely security-conscious was nailed with two separate BHO infections in the course of a week. So, for the time being, we default to ’Zilla, and only fire up IE for a few sites (like the Sohmer Family BLOG that won’t display or work correctly in Mozilla.