A blended threat is a computer network attack that seeks to maximize the severity of damage and speed of contagion by combining methods, for example using characteristics of both viruses and worms, while also taking advantage of vulnerabilities in computers, networks, or other physical systems. An attack using a blended approach might send a virus via an e-mail attachment, along with a Trojan horse embedded in an HTML file that will cause damage to the recipient computer. The Nimda, CodeRed, and Bugbear exploits were all examples of blended threats.