As the death toll in Lebanon and Israel mounts, the conflict has spilled onto the internet with sudden fury as gangs of computer hackers mount a withering cyber attack on thousands of Israeli and Western websites.

"This is definitely the biggest ever politically motivated cyber protest we’ve ever seen," Roberto Preatoni, a founder of Zone-H.org, a web-based crime observatory, told me. He said that as many as 10,000 web sites belonging to commercial, government and military web sites may have been caught in the crossfire.

The daily tally of sites being sabotaged is nearly 4,000, twice the normal number, according to Mr Preatoni. About 80 per cent of the attacks involve hackers reacting to the conflict between Israel and Hezbollah, and the overwhelming majority have been directed against Israeli, American and other Western sites, he said.

A team of Zone-H technicians collect and verify reports of sabotaged websites from both victims and hackers, giving Zone-H a unique vantage point on the activities of cyber protesters.

One minute the websites are a benign front door, selling insurance policies or detailing government services. The next minute, the official sites are ripped down and replaced by a digital protest, scrawled words pleading for an end to the war. One hacked site preserved by Zone-H.org carries the message:

Lebanon-israel...STOP!
No war
peace, that is all
This is a massive cyber-protest, we are :
Xtech Inc - eno7 - byond crew – Xarnuz
Join us !!

The hacked site, a Chilean IT vendor, appeared to be operating normally on Wednesday.

Disparate hacking groups banding together to deface websites in the name of a common cause is nothing new. Military clashes between Israelis and Palestinians, the war in Iraq and the Pakistani-Indian conflict over Kashmir have all provided ample fodder for cyber protests over the past six years.

Those cyber skirmishes were limited in scope, with the number of hacked sites relatively small, but the nature and severity of attacks began to change in February following the re-publication of Danish cartoons depicting the Prophet Mohammed.

The current Israel-Lebanon cyber protests have inflicted far greater collateral damage upon unsuspecting websites, Mr Preatoni said. Aside from thousands of small business sites (an easy target for a defacer), a large number of well-fortified web sites have been downed in the mêlée, including a website for NASA, Berkeley University and many military web sites, he added.

If your goal is to get your message of protest across to a global audience, defacing a popular website is a high-impact form of propaganda. "This is fast becoming the most effective way to protest, without a doubt," Mr Preatoni says. "You can do this anonymously, and you don’t have to leave your home."

The nature of the protest has become more elaborate too. In the past, a common defacement job was as thought-provoking as street graffiti. The perpetrator often would denounce his villain of the day – usually Mr Bush, Mr Blair or Mr Sharon – with a crude "F*** you" and sign off with his name and a tip of the hat to his loyal peeps, to whom he would no doubt brag afterwards.

Today, hackers are replacing pristine corporate web pages with gory images of maimed children and gun-toting soldiers bursting into homes. Also gone is the crude English. Indeed, the clarity of the message and tone indicates that cyber protesters are no longer enraged adolescents, but rather are impassioned activists. Think Proudhoun for the PlayStation generation.

The message may me be more polished, but the escalation is worrying. The protesters appear to be satisfied to make a point with words and images, but should they choose a more destructive approach, the consequences could be devastating. For example, should the hackers pool together to unleash a distributed denial of service attack to bring down, say, eBay or Haaretz the result would be a crippling outage.

Such tactics, though rather unsophisticated, are not currently part of the cyber protester’s handbook. Mr Preatoni has a theory as to why. "At the end of the day, hacking is all about ego. With a denial of service attack there’s no place to sign your name," he says. But he adds, "You’d be a fool to think they are not capable of such attacks."

A few more weeks of conflict and we may very well see just what they are capable of.

Bernhard Warner is a former Reuters internet correspondent in Europe and senior editor for The Industry Standard Europe. He writes about technology, the internet and media industries and can be reached at techscribe@gmail.com

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