Microsoft said it had seen more than 10,000 machines hit by the attack that, so far, it has not found a fix for.
Windows PCs falling victim will have control of that machine handed over to attackers.
Microsoft said the attacks had gone from theoretical to real very quickly and urged users to take steps to protect themselves.
Microsoft revealed the upturn in attacks in a blog post saying that it had been monitoring activity around the loophole since it was first revealed on 10 June.
Found by Google engineer Travis Ormandy, the loophole revolves around the Help and Support system built into XP. Mr Ormandy found that it was possible to exploit its ability to give remote aid and apply fixes to ailing machines.
Initially, said Microsoft, it only saw "innocuous" attacks by researchers attempting to replicate what Mr Ormandy had found.
Real exploits turned up on 15 June and these have been enthusiastically adopted by hi-tech criminals. More...
In the first ruling of its kind, the justices said they do, as long as there is a "legitimate work-related purpose" to monitor them. But the court said it would proceed cautiously in deciding how far an employer can go in searching the "electronic sphere" that has become an inescapable part of the modern workplace. More...
The backlash surprised the experts, who collectively go by the moniker Goatse Security. "We tried to be the good guys," said Escher Auernheimer, a member of the group. Drawing attention to the flaw, he said, "was the only way to get public notification."
For its part, AT&T reached out to iPad users bv email Sunday, blaming the incident on "computer hackers" who "maliciously exploited" an attempt by the carrier to speed the process of logging in to its website.
The comments were the harshest yet by the carrier, which apologized for the security lapse and said it would cooperate with any efforts to investigate or prosecute the breach. Goatse couldn't immediately be reached for comment on AT&T's remarks. More...
- Hackers Penetrate Google’s Building Management System
- Pentagon Accuses China of Cyberspying on U.S. Government
- Cheapest Way to Rob Bank Seen in Cyber Attack Like Hustle
- The global nature of advanced cyber attacks
- IBM executives head to Washington to press lawmakers on cybersecurity bill
- Cyber security bill pits tech giants against privacy activists
- China hacker's blog shows angst, and opens a window onto cyber-espionage
- Mandiant: Chinese hacker unit attempted to clean up online presence
- Cyberthreats getting worse, House intelligence officials warn
- Obama Presses Xi on Cyber Attacks Amid Focus on Hacking