A widespread spam campaign claims that a nuclear power plant on the outskirts of London exploded on Tuesday afternoon.

No such plant exists anywhere near London. The nearest is probably Dungeness B in south east Kent, some 77 miles (124km) by road from the capital.

The email claims to offer pictures of victims. In reality, the attached zip file is contaminated with a Trojan horse, identified by net security firm Sophos as Troj/Agent-HQE. Once the malware is installed, hackers can use it to spy on the victim's computer and steal information for financial gain.

The emails typically arrive with subject lines such as Reply: A report on radiation contamination of Canada, suggesting that a Chernobyl-style nuclear calamity has befallen the UK and local authorities have succeeded in hushing it up.

"Rather than use a real life event, the hackers have turned to fictional explosions and conspiracy theories in the hope they will strike a nerve with potential victims who will then click on the attachment without a second thought," commented Graham Cluley, senior technology consultant at Sophos.

Earlier this week virus writers distributed a contaminated email purporting to contain pornographic footage of presidential hopeful Barack Obama and a Ukrainian woman of easy virtue. A poor-quality porno clip - not featuring Obama, we hasten to add - was actually offered up, but the main purpose of the attack was to spread a form of spyware designed to intercept bank login credentials.

The two attacks - together with older claims by the Storm Worm gang that World War III had broken out in the Middle East - led us to wonder what spam tagline people are most likely to open. Sophos's Cluley said this varied with what was currently in the news, but sport and sex lures were always popular.

"Even though there's a plethora of porn freely available on the net people are sometimes tempted to click on something they receive by email in the misguided belief that their anti-virus software will always protect them. Something that's unusual, topical or glamorous tends to incite interest. That's why the Anna Kournikova worm did so well," he added. ®