A virus scanner update from McAfee has caused havoc amongst Windows XP computers by incorrectly identifying part of the operating system as a virus.
The 5958 update identified svchost.exe as the wecorl.a virus. A while back, Microsoft shifted the majority of its internal Windows files out of .EXE files and into .DLLs. However, DLLs can't be run on their own, so Svchost.exe is a file that allows the system to run content that's in a .DLL file. McAfee removing it meant that none of those crucial internal Windows files could run.
Businesses were hit hardest, but a number of home users were affected too. Some businesses had to shut down entirely due to the bug, and likely won't be too happy with McAfee. However, the company removed the update within a few hours and released a fix for those affected by the problem, as well as a "sincere apology" for the inconvenience caused.