SAN FRANCISCO - Cyber crooks are trying to cash in on fascination with the US presidential race by sending trick email promising a sex video starring candidate Barack Obama, according to Sophos computer security firm.

Email recipients gullible enough to click on an enclosed link get to see a seemingly homemade sex video that doesn't feature the presidential contender but does secretly install malicious software on people's computers.

'This email has been spammed out widely across the Internet, claiming that US senator Barack Obama has been in a sex video while he was in the Ukraine and all you have to do is click on the link to view the movie,' Sophos technology consultant Graham Cluley said in a video posted on the firm's website.

'If you were to click on that link ... spyware is installed on your computer which steals your passwords and your banking information and sends it to cyber criminals.'

Ill-intended creators of malicious software are quick to seize on hot topics to dupe people into opening files or executing applications that allow stealth programs to invade their machines.

The tactic is referred to as "social engineering" because it involves fooling computer users instead of hacking past security software or firewalls guarding systems.

Ruses have involved sending bogus emails promising images or video of celebrities or from major disasters such as earthquakes, tsunamis or hurricanes.

'So next time you receive an unsolicited email don't just blindly click on it,' Cluley advised. 'You could be getting into danger.' -- AFP