Do you belong to a fraternity that wants to spend this Memorial Day weekend trashing a national forest? Or perhaps you’re a self-professed street artist who wants to make national parkland your new canvas? Better make sure your misdeeds don’t end up on social media—because a band of forest-protecting vigilantes might hunt you down.

University of Oregon’s Lambda Chi Alpha fraternity is currently under investigation after photos of a trashed campsite festooned with school and fraternity logos were posted on Facebook following an annual unofficial trip to Shasta-Trinity National Forest.

“They left an incredible amount of trash,” a spokeswoman for the park told the Oregonian.

One employee of the United State Forest Service said that this happens every year, and the Forest Service spends thousands of dollars and several days to clean it. But the swift hand of justice fell upon the alleged offenders this time because one viral Facebook post drew so much attention to it.

Social media’s impact on national and state parks has largely been seen as negative, from wild animal selfies to cactus graffiti to the gleeful destruction of ancient rock formations. But there’s a positive side, too: It’s just as easy to share these images and inspire others to commit similar acts of vandalism as it is for nature lovers to track down the people responsible for defacing their second homes.

Casey Schreiner, who runs the popular hiking blog Modern Hiker, didn’t set out to be an “outdoor vandalism whistleblower,” as he puts it, but in 2014, a friend shared an image from the Instagram account of an artist who went by the moniker “Creepytings.” Creepytings (real name: Casey Nocket) was on a tour of national parks, leaving her “art” along the way and documenting the illegal acts on her social media profiles. Schreiner went through her Instagram and documented it all. The resulting outrage from Schreiner’s post led to national media attention and Nocket’s identification several days later. Schreiner’s blog has since gone on to catch artist “Mr. Andre” (Andre Saraiva) defacing a rock in Joshua Tree.

Last month, actress Vanessa Hudgens paid a $1,000 fine after posting an Instagram of a carving of her and her boyfriend’s name into a rock wall in Sedona, Arizona. Nature-loving Hudgens fans shame-commented her until she took the post down, but not before it had been reported to park officials.

“The same photos that vandals post to show off their work are now the photos people use to track them down and eradicate those works — and utilizing that Internet Outrage Machine is a powerful way to ensure the media spotlight is blasted on the vandals,” Schreiner says.

The National Park Service seems happy to take advantage. Last month, Arches National Park put out a call on its Facebook page for information on the person or persons who carved up its Frame Arch.