By EAMON MCNIFF and ALEXA VALIENTE

The next time you purchase a product online, how sure can you be that you're buying the real thing?

Counterfeiters are now duping consumers with websites designed to mirror real company sites. Besides fake luxury handbags or watches, people can even buy fake viagra or fake software from these websites.

In some cases, the phony websites with more pictures and products for sale even look more elaborate than the actual website.

Lev Kubiak, head of the Intellectual Property Rights Center, told ABC News' "20/20? that the best way to tell a website is real is to "look at the manufacturer's website. Take a look at where these companies say their products are distributed."

Watch the full story on "To Catch a Fake" on ABC News' "20/20? on Friday, June 13 at 10 p.m. ET.

Below are images of real websites next to their copycat counterfeit websites. Can you tell which is the counterfeit website?

(Obtained by ABC News)

(Obtained by ABC News)

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The Beats by Dre website on the right is the counterfeit website, and the Rosetta Stone website on the right is the counterfeit website.