Late at night, on an anonymous online messaging board, a user is quietly posting the contents of a folder full of child pornography for everyone to see. And people do see it: most ignore it, a few close the browser in disgust, and some even encourage him to keep posting. But not everyone is standing by.

When he posts a picture of himself, that’s all the help they need. The secret side of the internet moves into action.

Internet vigilantism is what happens when a group of anonymous internet users work together to punish evil in the world and work towards the greater good. It’s a rare occurrence, because normally when an internet community decides to get together and support a cause, it’s a malicious or bizarre one — like in 2008, when the National Epilepsy Foundation website was hacked and replaced with flashing black and white lights. Or declaring war on the Church of Scientology. Or hacking into and ripping apart Myspace pages for no clear reason.

The unifying factor in these events is that they’re all part of what is known as Anonymous. Composed of an inexact, unspecific set of individuals from a variety of anonymous forums and image-posting sites, Anonymous has been called everything from “domestic terrorists” to “internet superheroes” to “the first internet superconscious.” When Anonymous mobilizes, the results are terrifying. In China, they have another name for Anonymous, based off of the group’s ability to track down anyone: “The Human Flesh Search Engine.”

A few years ago, some teenagers posted some Youtube videos, of themselves abusing cats. Well, if the internet superconscious exists, it likes cats. Despite the fact that the offenders were wearing masks, Anonymous was able to dig through sites like Facebook until they found the person in the video. Eventually, the teens’ phone numbers and addresses were posted online, and between constant spam and harassment by total strangers, the authorities were called and the cat was rescued.

Which takes us to a few months ago, when Zach*, a freshman, was browsing an anonymous image-posting board and saw a user posting child porn. “I posted some pictures of secret agents sneaking around, you know, lighten up the mood … and then he started posting stuff about how his manager was coming. Manager? What?” The poster revealed that he was working at a McDonald’s in Northern California. “He posted pictures of himself, he was at the drive-through. … someone got his iPhone’s GPS signal, then via some Google Map-ing, we found the McDonald’s he was working at. We called the cops, and … Well, I’m pretty sure [he was caught], because he stopped posting.”

If one posts pictures online, they can be found too. “Pretty much every picture contains metadata. Which includes the GPS [coordinates] of where it was taken, shutter speed, pretty much anything you want.”

Zach was quick to point out that it wasn’t just him. “It was all of Anonymous, working together.” He was unapologetic or sympathetic to claims that his actions were immoral or illegal. “If they’re posting the picture, they’re posting the metadata. They can decide to ruin it if they want, but since they’ve decided to leave it on, they’ve sent it to us.”

Internet vigilantism is a highly controversial sport. On one hand, child porn is horrible and illegal. On the other hand, the lengths vigilantes will go to is extreme. Consider the case of Dog Poo Girl, in Korea: a woman who refused to clean up her dog’s Number 2 off the floor of a subway. An onlooker got a few pictures of her, and the Human Flesh Search Engine activated. Within days, her address and family information was in the ether for all to see, and she was shamed into quitting the university she attended.

And most agree that this, to a degree, is unacceptable. “It’s like, in the name of being good, I’m just going to ruin this random person’s life,” sophomore Jocelyn Lee said. “Maybe they should put it into the government.”

“They’re doing it for the right reasons,” sophomore Asher Wycoff argues. Some think that if it were left up to the government, the outcome would be repression of free speech, and that Anonymous’ method is efficient, if brutal and sometimes illegal. The vigilantes, of course, can’t argue. And they don’t plan to stop. “If the police are [with Anonymous],” Zach said, “Then we have bigger problems.”

*Name has been changed