Think these sites are all overseas? Think again. While the actual location of the pharmacy is unknown, 49 percent of the companies are using US hosting facilities and services. The next highest location is the UK, with only 12 percent. Smith notes that many of the pharmacies are working through different countries with billing done from one country, hosting from another, and shipment from somewhere else.

For example, one online pharmacy allegedly based in Canada uses a Web hosting service in Russia, and has a phone number with a Texas exchange. The site only sells single doses and has false accreditation.

"That said, if the location is in the US, brand holders would have a much easier time taking legal action than trying to do something across national jurisdiction," Smith said.

The average drug at a non-VIPPS site is $2.54 compared with an official site that has prices at $10.54 on average. MarkMonitor purchased a number of products from the online pharmacies that it profiled, and plans to test the efficacy of the drugs if and when it receives them.

FDA recently said that it was doing everything in its power to stop illegal pharmacies. In June, it sent 25 warning letters to online companies engaging in fraudulent marketing of fake cancer medication. The agency also posted a list of signs that consumers could use to denote a potentially illegal Rx dealer.

"It's going to take a combination of both industry and government working together to clean this up," Smith said. "Gone are the days of Web sites with spelling errors and sloppy grammar—these sites look real. As a result they are prolific and are going to target brands that aren't aggressive in stopping them."

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