Programs designed to launch advertisements on infected computers and/or to re-direct search engine results to promotional web sites. Adware programs are often built into freeware or shareware programs, where the adware forms an indirect ‘price’ for using the free program. Sometimes a Trojan silently downloads an adware program from a web site and installs it onto someone’s machine. Alternatively, hacker tools, often referred to as Browser Hijackers, download the adware program using a web browser vulnerability.

Typically, adware programs do not show themselves in the system in any way. In addition, adware programs seldom come with a de-installation procedure and attempts to remove them manually may cause the original carrier program to malfunction.