Get breaking news alerts and special reports. The news and stories that matter, delivered weekday mornings.

The Federal Trade Commission announced a groundbreaking lawsuit Tuesday against a company it accuses of paying for fake Amazon reviews. But the agency may have a lot more work to do if it wants to end the scourge of fake online reviews.

An NBC News investigation found thousands of questionable reviews on Amazon, Yelp, Facebook and Google — and showed that it was possible to purchase hundreds of positive reviews within days for a new company that had never done any work.

On Google and Facebook, the profile photos of the reviewers helped expose many questionable reviews. The profiles used the likenesses of such actors and actresses Terry Crews, Megan Fox, Omari Hardwick and Abigail Breslin. Those celebrities all confirmed that they did not write the reviews in question.

Jason Brown runs the consumer advocacy website reviewfraud.org and said it's common for fake reviewers to use images of celebrities — often by accident.

Let our news meet your inbox. The news and stories that matters, delivered weekday mornings. This site is protected by recaptcha

"What they'll do is they'll create their account, do a Google search for headshots and when they're doing that to add it to their account, they'll get famous people by mistake," Brown said.

NBC News created a gardening business on Facebook and paid $168 to Web sites that promised to post positive reviews. NBC

Over on Yelp, photos again gave away the questionable reviews. In glowing reviews for a contractor in California, three users posted beautiful photos of what they said was the finished work. However, the photos are apparently not of the contractor's work, but stock photos that can be purchased from Getty Images and Shutterstock.

On Amazon, one reviewer had posted 676 book reviews in the past six months — every single one of them was four or five stars out of five. Many had the same generic text and a similar headline: "I really liked it!"

To see how businesses may be purchasing fake reviews, NBC News created a gardening business on Facebook and paid $168 to websites that promised to post positive reviews. Within 24 hours, the business had 999 likes and a few days after that, more than 600 five-star reviews. The reviews came from apparently fake Facebook accounts –- the profiles spread out across the globe. The reviews even include generic descriptions of the work such as "really efficient and a pleasure to deal with" and "very polite, did a wonderful job."

While the speed and volume with which the gardening business garnered raves may be shocking, Brown said the problem is common and out of control.

"It really is the wild west and there's no sheriff on duty," he said.

In statements, Facebook, Google, Amazon and Yelp all said they are aware of the problem and have protocols in place to actively monitor and remove fake reviews. They also said the public can help end the problem by flagging suspicious reviews.

Brown says consumers should be vigilant and avoid reviews with these red flags: