Microsoft issued a Security Advisory on June 10, warning of an unpatched vulnerability in the Windows Help and Support Center function in Windows XP.
Proof-of-concept exploit code for the vulnerability is now being used by hackers, who've started using it broadly. Microsoft Malware Protection Center, said "In the past week, however, attacks have picked up and are no longer limited to specific geographies or targets, and we would like to ensure that customers are aware of this broader distribution."
Holly Stewart, said "over 10,000 distinct computers have reported seeing the attack at least one time. Hackers initially began targetting systems on June 15 but in limited numbers."