A battle among hackers erupted on the Internet as some factions disrupted a loosely coordinated "contest" among other groups trying to vandalize thousands of Web sites around the world.
Unknown attackers knocked offline for most of Sunday an independent security Web site, zone-h.org, that was verifying reports of online vandalism and being used by hackers to tally points for the competition.
At least three such vigilante-style attacks forced the hacker organizer, who identified himself only as "Eleonora" to extend the contest until 6pm Sunday. But with disruptions preventing vandals from claiming credit for their break-ins, experts said it could be days before damage from this weekend's hacking would be known.