Cat videos are all the rage on YouTube, so much so that a Russian company hijacked a recent cute clip of a feline named "Pepper" in order to steal the ad revenue.

Kidnapping YouTube videos, which anecdotal evidence suggests has happened thousands of times, is as easy as it gets.

A Russian company called Netcom Partners and others are taking advantage of YouTube's copyright-control filters, known as Content ID. It's not clear how much money the scammers are stealing from YouTube videomakers. But if you judge by the volume of complaints about the hijacking on Google's forums, it's likely Netcom and others are doing pretty well making money for nothing.

"YouTube has developed some system that allows these companies to hijack videos for revenue for content that is not their own without any legal oversight," Justin Pye, an Emory University physics doctoral student who produced the Pepper video, said in a telephone interview. The 83-second homemade spot has attracted more than 149,000 hits.

Matt Metford, a 27-year-old Vancouver, B.C. high school teacher, said he has been victimized about 20 times since March. His uploaded videos show snippets of video gameplay overlaid with Metford dictating a fake story about the game's action in a monotone voice.

"This is a form of cyberbullying," he said in a telephone interview.

Here's how it happens.

To assuage copyright concerns, Google-owned YouTube has engineered a filtering system enabling rights holders to upload music and videos they own to a "fingerprinting" database. When YouTube account holders upload their videos, Content ID scans new uploads against the copyright database for matches.

If a full or partial match is found, the alleged rights holder can have the video automatically removed, or it can place advertising on the video and make money every time somebody clicks on the video.

The idea was to solve the problem of large copyright holders constantly complaining about copyright violations. The compromise lets people submit homemade videos set to one of their favorite musicians' songs or a snippet from a movie and allow the original creator to benefit from the exposure and ad dollars if they so choose.

But if Content ID overmatches or a rogue manages to feed the filter content it doesn't own, a YouTube user could see her video hijacked through a false copyright claim.

That's what Metford, Pye and countless others say has happened to them. Out of nowhere, different ads started appearing on their videos, and the revenue wasn't going into their accounts.

Content ID largely works on auto-pilot.

When Content ID finds a match between videos, the uploaders receive an e-mail from YouTube informing them only of the name of the company claiming a copyright breach. Unless the uploader files a counter-notice disputing the copyright violation charge, the claimer gets control of the video. The scammers seem to be hoping that a copyright claim from an official-sounding company sounds scary enough that users won't protest.

In most every case, when a victim files a counter-notice, Netcom and others abandon their claims, and the original video maker wins back complete control of their work.

Netcom's website http://netcompartner.com (cache) alternately placed its base of operations in Malaysia and Switzerland, though it is registered in Cyprus.

The site has been emptied of content and taken down. Netcom did not respond to a request for comment. A now-vanished older cache of the site showed the company signed up YouTube users, promising to create a network that would boost all of their page views. Though the website identified the company as Netcom Partners, the infringement notices to YouTube users simply use the generic name Netcom.

Google only allows large media companies and video networks to join the Content ID program, which has about 2,000 registered participants. Netcom has been claiming copyright to material it does not own.

Google says its filters have six million reference files. Following its 2007 deployment, it has matched against 120 million videos.

"Our Content ID system works by checking user-uploaded videos against reference files provided by rights owners prior to publication on YouTube," spokeswoman Annie Baxter said in a statement. "If the system finds a match, the rights holder determines the policy applied to that video – either block, track, or make money from the video using ads. Partners found to be abusing or attempting to abuse Content ID will be subject to disciplinary action, including the possibility of account termination."

YouTube forums are littered with complaints by disgruntled YouTube account holders.

Google declined further comment. The search giant said company policy prohibited it from saying whether YouTube was even aware of the situation, and whether it has ever taken action against any company for abusing Content ID policy.

For Google, inaction has little consequence. The ad giant gets its cut of ad revenues from YouTube videos before the content producers do. From a bottom-line perspective, it doesn't matter who gets the other – the maker of the cat video or some fly-by-night hijacker.

Sometimes, however, there are honest mistakes because of the way the filters work on auto-pilot.

TorrentFreak, for example, points out the situation of Dutch game-review site Gamer.nl, which says Google's filters have falsely assigned it ownership to as many as 10,000 user-generated videos.

"It appears that the Content-ID filter is automatically assigning these videos to Gamer.nl, because the clips produced by the review site also include snippets of trailers and in-game play. In other words, the Content-ID filter is set so broad that official game trailers are assigned to Gamer.nl because Gamer.nl uses footage from the trailers in its reviews," TorrentFreak wrote.

Under U.S. copyright law, Google is not required to deploy copyright filters. But rights holders are embracing it as a way to make money online. Even Viacom, which is suing YouTube for $1 billion for copyright violations, uses Content ID and its lawsuit only covers alleged copyright violations before the filter's deployment.

But regular YouTube users – the ones who make what's often called user-generated content – aren't quite so happy with the system.

Patrick McKay, a Regent University School of Law student in Virginia, said he has been victimized by the filters. He even started his own website about it called FairUseTube.org to inform YouTube users how to fight the claims.

"More and more," he said in a telephone interview, "I'm seeing issues with people making original content, and it gets claimed by some random obscure company, using Content ID, and saying they own the copyright."