"LinkedIn users expect to be contacted by recruiters, so this ruse works out in the scammers' favour," it said in its report.

"Most of these fake accounts have been quite successful in gaining a significant network - one had 500 contacts. Some even managed to get endorsements from others," Symantec researcher Dick O'Brien told the BBC.

In response LinkedIn said: "We investigate suspected violations of our Terms of Service, including the creation of false profiles, and take immediate action when violations are uncovered.

We have a number of measures in place to confirm authenticity of profiles and remove those that are fake. We encourage members to utilise our Help Center to report inaccurate profiles and specific profile content to LinkedIn."

The researchers found that the fake profiles tended to be made up of text that had been copied and pasted from the profiles of real professionals. They used photos, often of women, pulled either from stock image sites or of real professionals.

They also used keywords such as "reservoir engineer", "exploration manager" and "cargo securement training" which are likely to gain them visibility via the site's built-in search engine.

Many of the terms related to the logistics, information security and oil and gas industries, Symantec said.