Anti-pedophile activism encompasses opposition against pedophiles, against pedophile advocacy groups, and against other phenomena that are seen as related to pedophilia, such as child pornography and child sexual abuse. Much of the direct action classified as "anti-pedophile" involves demonstrations against sex offenders, groups advocating legalization of sexual activity between adults and children, and internet users who solicit sex from underage teenagers.
Some local groups have taken to marching in opposition to the locations of various child sex offenders. In the Netherlands, the paedophile activist group Vereniging MARTIJN has been protested against by the far right Nationale Alliante. There have been incidents in which vigilantism intended to be against paedophiles has been mistakenly directed against the wrong person, including one concerning a man with the same surname as a locally known paedophile , the persecution of a pediatrician, due to ignorant misinterpretation of his job title  and an incident where a man was identified as a paedophile because he was wearing a neck brace similar to the one a sex offender was wearing when pictured in a newspaper.
Perverted-Justice is generally an anti-hebephilia organization with the stated mission to expose and convict adults who solicit and groom pubescent or post-pubescent minors on the Internet. While the organization typically goes after adults seeking teenage individuals under the age of consent, they also consist of volunteers who carry out sting operations by posing as 10-12-year-olds. After obtaining identifying information from these men, who may offer their telephone numbers and other details so that meetings can be arranged, the organization passes the information on to law-enforcement. Some administrators of Perverted-Justice.com launched CorporateSexOffenders.com, and its associated wiki project "Wikisposure," in June 2007, which aim "to target corporations and the pedophiles they allow to use their services." The Wikisposure project later moved to its own domain, Wikisposure.com.
Other anti-pedophile activist groups
Another initiative, Predator Hunter, headed by Wendell Kreuth, aims to track down and expose the pornography-related activities of alleged 'sexual predators'. Although, in 2002, Kreuth disclosed details of his activities in an interview with Minnesota Public Radio (Note: the websites featured in the article are, in fact, legal), the activities of Predator Hunter in the years prior have garnered more attention, particularly in relation to Bradley Willman, whose anti-pedophile activism is described below:
Between 1997 and 2001, Brad Willman was known as Omni-Potent, an Internet vigilante who would track pedophiles by spending 16-plus hours a day hacking into people's computers from his parent's house in Langley, a suburban community just outside Vancouver. Ultimately, he was responsible for the arrests of about 40 pedophiles across Canada and the U.S. Willman's successful, albeit unpaid and short-lived venture as "Citizen Tipster," as he was known by police, is now over. But his activities have sparked intense debate over the legality of his tactics.
He would verify where suspects were from, and send the information on to Predator-Hunter, an online pedophile watchdog group that would, in turn, send it to other sources to be verified before passing it on to police. "Parents in a number of countries, I think, owe OmniPotent a debt of gratitude for what he did," says Wendell Krueth, president of Predator-Hunter. The end justifying the means is a concept Predator-Hunter supports. "We don't tell people to go hack, but we consider whatever information we get worthy in taking down pedophiles," Krueth says.
Silentlambs and LambsRoar are both web-based anti-pedophile groups that seek to protect children through education, to provide legal assistance, and to provide assistance to victims [survivors] who have been molested as children and silenced from speaking out or seeking proper assistance as directed by religious authorities. To date, most emphasis has been on abuse within the Jehovah's Witness community.
Members of Anonymous were identified as responsible for the arrest of suspected pedophile Chris Forcand. They contacted the police after some members were "propositioned" by Forcand with "disgusting photos of himself". Anonymous were described as "cyber-vigilantes who seek to out anyone who presents with a sexual interest in children".
Criticism of tactics
A representative of the National Center for Missing and Exploited Children's Exploited Child Unit has stated that the NCMEC does not condone investigations by citizens because according to the NCMEC, those actions do not deter predators and can push the predators to move to other locations and become more effective at hiding their identities. The internet safety organization CyberAngels, an offshoot of the Guardian Angels echoes similar concerns. Police officials in the past have been opposed to working with such groups, or have done so only reluctantly. 
- Anti-pornography movement
- Chris Forcand
- To Catch a Predator - An NBC Dateline series that collaborated with Perverted-Justice
- John Wojnowski
- Families flee paedophile protests August 9, 2000, retrieved May 21, 2007
- Dutch paedophiles set up political party, May 30, 2006, retrieved May 22, 2007
- Plain stupid by Salon.com
- Pediatrician attacks 'ignorant' vandals by BBC News
- Mob mistakes man for sex abuser by BBC News
- Vigilante attack on innocent man by BBC News
- Perverted-Justice.com, Official website
- Corporate Sex Offenders, retrieved June 25, 2007
- Chasing online predators, April 15, 2002, retrieved May 21, 2007
- The Big Chill: Verizon's decision last month to shut off a Montreal ISP for hosting edgy gay chatboards points to a colder, grayer internet ahead, November2006, retrieved May 21, 2007
- Howard, Cori. "Internet Vigilante." Maclean's, Vol. 118, Issue 23 (2005), pgs. 56-57 
- See also Casey, Eoghan, Digital Evidence and Computer Crime: Forensic Science, Computers and the Internet. London: Academic Press, 2004. pg. 580 
- Howard, "Internet Vigilante", pg.56
- "Jehovah's Witnesses Settle Abuse Cases." French, Rose. Associated Press (May 10, 2007)
- Gus Kim (reporter) (2007-12-08). "Internet Justice?". Global News (CanWest Global Communications).
- Constable George Schuurman, Public Information, for Detective Constable Janelle Blackadar, Sex Crimes Unit (2007-12-06). "Man facing six charges in Child Exploitation investigation, Photograph released, Chris Forcand, 53" (PDF). News Release (Toronto Police Service). Archived from the original on 2008-02-27. http://web.archive.org/web/20080227214335/http://www.torontopolice.on.ca/newsreleases/pdfs/13073.pdf. Retrieved 2008-02-25.
- Jonathan Jenkins (2007-12-07). "Man trolled the web for girls: cops". CANOE (Toronto Sun). http://cnews.canoe.ca/CNEWS/Crime/2007/12/07/4712680-sun.html. Retrieved 2008-02-19.
- Daniel, Mac, "Vigilante Websites Combat Solicitation of Minors for Sex", Boston Globe. Oct 11, 2003. pg. B.3
- Colgin, Chris and Jason Trahan, "Campaign against Child Sex Predators Draws Critics", Dallas Morning News. Sept 11, 2006
- Measurement and Analysis of P2P Activity Against Paedophile Content
- Internet Watch Foundation
- Association of Sites Advocating Child Protection
- "Counter-terror methods used online to trap paedophiles" Guardian UK technology article
- The Lucy Faithfull Foundation