When Himesh Kar, a film producer, recently replied to an e-mail apparently sent from his associate Jon Thompson, via LinkedIn, he was surprised to find confidential information about his new film The Bengali Detective appear shortly afterwards on what was apparently Mr Thompson’s Twitter feed.

But further inquiries revealed the indiscretion had not been perpetrated by his friend. Instead, Mr Thompson, head of European business at Reliance MediaWorks, a film production company, had been the victim of an imposter who had set up a LinkedIn account in his name, as well as a Twitter account and a blog.

“I already had a LinkedIn account with several hundred contacts,” says Mr Thompson. “But within four days this person had linked to around 1,000 people, including some quite prominent people in Hollywood. They just thought I’d deleted my old account and set up a new one.” The impersonator started arguments with LinkedIn contacts, and sent racist abuse and homophobic rants.