Remember how I said that the web is changing and so is the threat landscape? Well, that's true, except for one thing though - NetSky seems to be the most widely spread virus out there and nobody can take that title away from[admark=1] it.
"Email-Worm.Win32.NetSky.q", as it has been dubbed by Kaspersky experts, is the most widely spread threat out there in the month of September too. 25.22 percent of virus infections had NetSky.q written all over them. However, there are more types of Netsky - there is also the .aa version, as well as .t, .b, .x and others. Just take a look at this chart and see how viruses ranked in September.
For those of you that have no idea what NetSky is and what it does, allow me to explain it to you. It's a family of computer worms that spreads like crazy. And it is so popular because it removes other viruses, so once you've got it on your machine, you won't have any trouble with Bagle and MyDoom. That's why it's more prolific than other viruses. It popped up at the beginning of 2004 and is authored by the same guy that wrote the code for the infamous Sasser virus.
So, what else does it do besides making sure the machine is all his? Well, it will "read" your e-mail contact list and send messages with an attachment to all your contacts. Of course, the attachments are infected with NetSky and once the user downloads them, it will also get the virus. So, yes, it's mail spread. This is just another reason why people are advised not to click on links in spam e-mails and to be careful when downloading attachments, because, not only could one get a virus on his/her machine, but he or she will also send it (involuntarily, of course) to friends and other contacts.