Security specialist Sophos is warning internet users in Australia and New Zealand to avoid being sucked in by spam preying on people's fears about bird flu.

Australian computer users receive three times more spam emails from the US than from any other source, according to statistics from security developer New Millennium Solutions (NMS).

Last month saw an increase in spammers using legitimate websites as jump off points to avoid anti-spam defences. According to a new report, spammers put links on sites such as Yahoo! and Geocities, which when clicked on take unsuspecting users to spam sites.