Blended threats use a combination of different malware techniques in an attack.

Virus and spyware writers, spammers and phishers often collaborate to create blended threats. These threats are increasingly surreptitious and low-profile, mutating in hours or even minutes in order to evade detection. They are also often financially motivated.

An example is the Storm worm (also known as Dorf and Dref). It started with a vast number of spammed-out malicious e-mails. Clicking on a link in the e-mail took users to a webpage containing a malicious script that downloaded a Trojan, which took control of the computer. The computer could then be used to spam out more malware and junk mail, or to launch a distributed denial-of-service attack.

An integrated security approach that protects against spam, viruses and other malware is important to defend blended threats. Because of their ability to change rapidly, it is also important to implement proactive detection and protection that identifies and stops threats before the launch.