That $2,000 Louis Vuitton handbag advertised on Facebook for just $239? Yeah, it’s too good to be true. New research by Andrea Stroppa and Agostino Specchiarello, both of whom are cyber-security experts, found that about a quarter of the fashion and luxury ads they examined on Facebook are for knockoffs.

The ads, touting things such as $180 Ray-Ban Aviator eyewear for less than $30, linked to bogus e-commerce sites registered by Chinese front companies. (Milan-based Luxottica Group, the world’s largest eyewear maker and owner of Ray-Ban, says it’s working with Facebook and urges the company to do more.

“The fight against counterfeiting is a priority for Luxottica,” a company spokeswoman said). Stroppa and Specchiarello’s research is based on a review of more than a thousand ads, including 180 in the category of luxury and fashion. Of those, 43 pointed to counterfeit goods.

For years now, fraudulent Web links have been a battleground for luxury companies. Last September, Paris-based LVMH Moet Hennessy Louis Vuitton ended a longstanding dispute with Google, agreeing to work with the search giant to help prevent vendors from advertising counterfeit goods online. LVMH, the world’s largest luxury-goods company, had accused Google of violating its trademark rights by selling protected words as keywords that then link users, who search under the French company’s brands, to websites selling fake items.

Websites that sell counterfeit goods often look very similar to the real thing. For example, a rather convincing knockoff Ray-Ban storefront includes the brand name in the Web address, designs and logos resembling, and information about nonexistent warranties, according to the researchers.