Spammers posting third-party links on Facebook earn about $200m per year, according to Italian security researchers.
Researchers including Andrea Stroppa and Carlo De Micheli, had analysed the social network for phrases including 'Hey click here for a free iPhone' followed by a link directing to other site.
The research also involved searching for posts incorporating keywords such as 'click here', 'free', 'wow', or 'join', followed by short links.
De Micheli was quoted by the Guardian as saying that the spam posters get paid an average of $13 per post, for pages that have around 30,000 fans, up to an average of $58 to post on pages with more than 100,000 fans.
"If we consider these two as extremes, the pages we analysed generate a revenue of 18,000 posts per day, times the revenue per post - ranging from $13 to $58 - 365 days a year," De Micheli said.
The research also found that spammers tricked Facebook users by setting up a fake fan pages and asking them to click on the links.
About 20 websites were even discovered, where spammers set deals to post spam links on the social networking site in return for cash.
"Third parties pay spammers to post their links on Facebook pages, to reach the largest amount of users possible," De Micheli said.
"We notice that it is rather common for the landing page [from a link] to be a product on an e-commerce site made to monetise quickly rather than to generate traffic on a home page.
"Links to YouTube can be used to generate views, and so money generation on YouTube is a fast-growing market."