If the following applies to you:
- You have Internet Explorer 6
- You don’t use Windows XP, or you haven’t installed XP Service Pack 2
- You visited The Register between 6am and 12:30pm GMT on Saturday morning
then it is possible that you may have been infected with the Bofra worm. This worm spreads through a flaw in Internet Explorer, which so far has only been fixed for users of Windows XP SP2. Users who have yet to install SP2, or who use IE on another version of Windows, may well have been infected with Bofra.
I would urge you to run a virus scanner to make sure you were not infected. Here is an official explanation from El Reg – the offending adverts were provided by a third-party advertising company which El Reg has suspended dealings with for the time being.
The fact that this is a third-party company makes this more worrying as other sites may well be affected too. I urge you not to use IE and instead use a browser like Mozilla Firefox or Opera for the time being.
Update: Falk, the company concerned, has issued a statement. It appears that one of their load balancers was hacked.