Blended threats is a general description for malicious programs or bundles of malicious programs that combine the functionality of different types of malware: viruses, worms, Trojans and so forth.

As applications and operating systems as well as security products have become more sophisticated, virus writers have retaliated by creating more and more complex malicious programs.

A malicious program needs to meet most of the following criteria to be called a blended threat:

• Have more than one payload - launch a DoS attack, install a backdoor, damage a local system etc.
• Replicate and/or spread in a number of ways - via email, IRC channels, file-sharing networks, download copies of itself from compromised web sites etc.
• Use multiple attack methods - infect exe files, modify more than one registry key, modify HTML files etc.

Read more:

• About Trojans
• About worms
• About social engineering