Their British leader and founder, Colin "Gabriel" Hatcher, once a Guardian Angel in London, says they are trying to "help people in trouble". This means tracking down stalkers, fraudsters and hackers, and most of all, "paedophile predators".
Instead of making online citizens' arrests, the most that CyberAngels can do is report criminal activity to Internet service providers and sometimes the police. "We are not some kind of SAS organisation," insists Hatcher. "Mainly what we're doing is witnessing crimes and passing it on to the authorities."
In America, police and FBI have said that the CyberAngels may actually be hindering law enforcement. The FBI has said that they are in danger of interfering with their investigations, especially when they pose as children in the hope of attracting paedophiles, a tactic employed by the FBI.
But Hatcher says the CyberAngels only want to help to enforce the law. "This is still a very new field and the FBI doesn't have the resources to deal with the scale of the problem. We, the people, need to help the police do better."
Civil liberties groups also voice concern. Declan McCullagh, a Washington journalist and Fight Censorship campaigner, is no fan. "I don't think what they do is worth very much," he says. "They say they're in favour of free speech, but if you look at their actions, it's just not so. They tend to think everyone is a villain and out to do wrong. And they have a very broad definition of what is `wrong'."
The CyberAngels do indeed veer towards the moral high ground, often blurring the line between what is actually illegal and what they deem immoral. Despite Hatcher's insistence that all they do is report crime, he also talks of "investigating" people's movements on the Net.
He describes a recent case where an American woman became involved with a British man who, after gaining her trust and persuading her to send him nude photos, allegedly threatened to post them on the Internet if she didn't agree to send photos of herself in bondage. The CyberAngels helped her to contact Scotland Yard. But Hatcher says they also "helped obtain a lot of information about the man. We researched what he was doing on the Internet and found a lot of information about him among the bondage groups".
The CyberAngels argue that they are backed by popular demand. Hatcher says that when the Internet began to explode in 1995, the Guardian Angels received hundreds of letters from concerned parents: "The message was `we need you'."
Sceptics dismiss the Angels as being an ongoing publicity stunt, however. Their approach to crime is also criticised for being simplistic. Hatcher talks a lot about "the good guys" and "the bad guys". But as Declan McCullagh says, it's not that straightforward. "The pornographers are quite happy to label their sites and keep kids away," McCullagh says. "As for the so-called paedophiles, I suspect a lot of them are journalists and policemen looking for stories and arrests."
Britain now has its own Internet watchdog, the Internet Watch Foundation. It has been up and running only a few months and has so far received few calls from people wanting to report illegal activity. Although the IWF may be less showy than the Angels, it has the backing of the Metropolitan Police and the majority of Internet service providers.
But both the CyberAngels and the IWF are going to have problems assessing their success. Unless the evidence they find leads to prosecutions, it's hard to know exactly how useful they are. The CyberAngels say they have already passed on more than 5,000 pieces of evidence to the authorities. But they have no idea how many "bad guys" they've managed to stopn
Internet Watch Foundation (01223-236 077 or firstname.lastname@example.org)