Last year's constant onslaught of high-profile viruses cost the industry over $13bn, according to research from Computer Economics.
Antivirus firm McAfee.com claims that the effectiveness of these malicious codes was due to a one-two punch of traditional virus attributes combined with hacking techniques. The industry has dubbed this new wave of attacks "the hybrid threat".
"Hybrid threats are the next generation of digital vulnerability," said Sam Curry, security architect at McAfee.com.
Users have seen the disastrous impact of the hybrid threat in the aftermath of Code Red, and the Goner and Qaz worms.
All these viruses not only propagated across computers, they left back doors or hijacked machines for later use in denial of service attacks.
But users should also be on the lookout for subtle social engineering viruses, such as an email arriving with the subject "Hi, how's it going?" rather than "Naked pics of Anna Kournikova".
McAfee.com virus research manager April Goostree said: "Today PC users aren't looking out for the usual, they are looking for the unusual and this can make them vulnerable to viruses delivered in an ordinary way."
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