The next email greetings card you get may come with a nasty surprise. According to internet security vendor SurfControl, attackers are increasingly using fake cards as a way of installing malicious software.

This practice is up by about 90 percent from last year, and greetings cards now make up more than half of all malicious email being sent, according to SurfControl.

The number of ‘phishing’ attacks, in which users are tricked into entering personal information on fake websites, is also on the rise. But increasingly attackers are looking for ways to trick users into downloading software that can be used to take over a computer, turning it into a so-called ‘zombie’ machine.

Often this can be done by sending an email greeting that entices users to click on a maliciously encoded web page. Another trick is to mask an email message so it appears to originate from the user's IT department.

Overall, malicious email was on the rise during the second quarter of 2005. SurfControl said its email filters tracked about 30 percent more such messages than during the same period last year.