Industry experts warned today of a "dramatic increase" in online identity theft over the past two years.

A new report from McAfee said that the instances of key-logging malware to capture passwords and other private information increased by 250 per cent between January 2004 and May 2006.

Additional findings from the security firm's research show that the number of phishing alerts tracked by the Anti-Phishing Working Group has multiplied 100-fold over the same period of time.

"Identity theft is a global phenomenon that threatens all of us, which means we all need to become more aware, more vigilant and less trusting to protect ourselves," said Jeff Green, senior vice president of McAfee's Avert Labs.

"By learning where we are vulnerable, and how and why criminals engage in identity theft, we can take the necessary precautions to avoid being victimised. "

The study reports that identity theft exacts a "high toll" on national economies around the world. According to the US Federal Trade Commission, the annual cost for consumers and businesses in the US alone reaches $50bn annually.

In the UK, the Home Office has calculated the cost of identity theft to the British economy at $3.2bn during the past three years.

Some estimates from the Australasian Centre for Policing Research place the cost of identity theft at $3bn each year.