Wondering if you've been hit by the Conficker worm? Here's a "Conficker Eye Chart", an ingeniously simple web browser test created by Joe Stewart which takes advantage of the way the worm works.
Just follow the link above, which loads a webpage with six logos. If you can't see one, or any of the logos in the top row, then you are almost certainly infected by Conficker or other malware. This is because the Conficker worm (or other malware) will attempt to block any connections to anti-virus software company servers.
Stewart originally hosted the "eye chart" on his own server; it is now hosted by the Conficker Working Group, which is led by Microsoft and a number of anti-virus/ computer security software companies.
I was quite amused that Stewart had the opportunity for a little Unix advocacy. The other test images on the "eye chart" are the logos for Openbsd, Linux, and FreeBsd, and are linked to their respective websites. The worm, BTW, only infects Windows boxes.
If you suspect an infection, try using any of the repair tools from the Conficker Working Group.
In related news, there was some Conficker-themed geek humour going around on April 1.