A Turkish online vandal breached the security of a group of Web servers hosting more than 38,500 Web sites in less than a day, vaulting Turkey past Brazil as the source of most defacements, watchdog Zone-H.org stated on Thursday.

The vandal, who uses the handle "Iskorpitx," originally tagged about 21,500 Web pages and then, a few hours later, defaced another 17,000, Zone-H.org said in a statement. The watchdog site--which hosts copies, or mirrors, of defaced sites--had trouble keeping up with the pace of defacements, said Roberto Preatoni, founder of Zone-H.org.

"We have never seen anything like this before," Preatoni said.

Defacements, a much reported crime earlier this decade, have largely become an underground game of oneupmanship, continuing to grow in prevalence: Nearly 500,000 sites were tagged in 2005, a third again the number in 2004, according to Zone-H.org. In a recent trend, some online vandals have taken to vigilantism, defacing the Web sites set up by fraudsters as part of phishing attacks.

While many defacements in Turkey have a pro-Islamic motive, Iskorpitx in general does not seem to be driven by religion, according to Preatoni. The online vandal specializes in defacing Windows-based Web servers, with nearly 95 percent of the site's defaced by the vandal running on Windows. In the latest spree, the vandal tagged second-level pages, not sites' home pages.

With the defacements, Turkey-based vandals now account for more than half of all defacements, overshadowing Brazil, according to Zone-H.org.