'Hacktivists' armed for Christmas cyber attacks

US data security company Imperva says downloads of the attack program used to bombard websites with bogus requests for data have jumped to over 40,000, with thousands of new downloads reported overnight.

"It's definitely increasing," said Imperva web researcher Tal Be'ery.

The freely available software, dubbed "Low Orbit Ion Cannon," is a critical part of the campaign by "hacktivists" seeking to take revenge on sites they believe have betrayed WikiLeaks, which has outraged American officials by publishing hundreds of thousands of classified US diplomatic cables.

Users who download the software essentially volunteer their computers to be used as weapons that volley streams of electronic spam at targeted websites. The more computers, the better chances are of overwhelming the targeted website.

The cyberguerillas, who gather under the name Anonymous, have had mixed results. Attacks directed at the main pages of Visa and MasterCard succeeded in making them inaccessible, in MasterCard's case for several hours.

Attacks on online payment company PayPal have periodically rendered a small part of its website inoperative.

But other planned onslaughts, on London-based Moneybookers.com or Amazon.com, have either fizzled out or been called off.

All five sites have severed their links to WikiLeaks recently, many citing suspected "terms of use" violations.

The moves angered WikiLeaks supporters and alarmed free- speech advocates, many of whom claim that the companies are caving in to US pressure to muzzle the website.

WikiLeaks distanced itself from Anonymous, saying "we neither condemn nor applaud these attacks.