Some searches for news about the earthquake and tsunami yesterday directed people to a legitimate website owned by an ill-prepared US construction company.

From there, they were seamlessly hijacked to an infected site with a Chinese web address.Ironically, the second site warned people their computer was at risk of a virus and offered to install software to protect them. The so-called security software was itself a virus.

A security expert at the anti-virus company F-Secure, Chia Wing Fei, said the scam took a circuitous path through several countries to avoid detection before it urged people to install the rogue software.

Once in place, the software opens a back door to a computer so hackers can steal information and deploy the computer as part of a cyber army for other malicious purposes.Mr Chia said: ''They're no longer doing one specific purpose. They could be doing multiple stuff because they have a way of communicating back to a command and control centre.''

The Samoan scam is not new. Criminals used similar strategies after the deaths of Michael Jackson and Patrick Swayze, and the practice was proving successful enough for criminals to continue using it, Mr Chia said.F-Secure also reported evidence of Twitter ensnaring the unwary.

Twitter's use of short, indecipherable web addresses can help disguise a criminal's intent.

Mr Chia said the virus on the Chinese site, while not entirely new, had been altered enough to evade anti-virus software that had not been updated.He said Google had removed at least some of the fraudulent sites from its search results.