I don't think this is an April Fools' Hoax.
The Microsoft Security Response Center blog reports that they "have been working around the clock to test this update and are currently planning to release the security update that addresses this (ANI) issue on Tuesday April 3, 2007."
This is further supported here: www.microsoft.com/technet/security/bulletin/advance.mspx
Apr 2nd 2007
1 decade ago