Anti-virus programs becoming less effective
According to studies done by a German computer magazine in 2007, the 17 different anti-virus programs they tested only detected only 20-30% of the malware they introduced on the computers. In 2006, a similar study yielded much better detection rates of 50-60%.
These results are not encouraging and seem to indicate that anti-virus programmers who update virus definition files are not able to keep up with hackers and malware creators. Also, the “bad guys” have easy access to the same anti-virus programs and even free online services that test suspicious files, and thus they are able to test if their creations can get through the latest anti-virus programs before they release them.