The call, when it comes, is both unexpected and worrying to its American recipients. "Your computer and IP address have been noted as visiting the WikiLeaks site," says the recorded message. The penalty for doing this: a $250,000 or $25,000 fine, and the possibility of imprisonment. But it does leave a number to call where the fine can be paid – with a reduction for prompt settlement and without the unpleasantness of a court case.

For Americans, whose airwaves have been filled with people proclaiming that the WikiLeaks site is somehow breaking the law and a threat to the US, with federal workers being warned not to visit the site while using work computers, and the US government issuing subpoenas for the records of some of the 700,000 people who follow the WikiLeaks Twitter account, the message may sound plausible enough to act on.

But that would be a mistake. For the call is just the latest manifestation of fraudsters' well-known ability to pick up on concerns and milk them. The Spokane arm of the US's Better Business Bureau, an independent organisation which accredits businesses, has warned people to beware of the scam.

"It was only a matter of time before clever scammers would reveal a 'latest' approach at attempting to part people with their money in 2011," notes the organisation. "If you are military personnel, this type of call could seem very real or hold more significance because the US Pentagon openly banned military personnel from visiting WikiLeaks for security reasons."

Indeed, it's not only the military: federal staff were told in December they may not access the site because its information is formally classified – despite more than a million US staff having fully authorised access to the content of the cables that were leaked. The Library of Congress also banned access, and students at Columbia University were told it could harm their job prospects if they accessed the cables.

All of which has created the perfect climate for fraudsters, who as ever know that you can't con an honest man – but that you might be able to con a worried one. So far there are no confirmed reports of anyone actually falling for the scam.

Then again, they may have been told they're not allowed to speak about it because or they'll be guilty of treason. The ways of scammers are subtle indeed.