Adware

In short: Adware shows unwanted advertising, often with data collection or further malware in tow.

In more detail: It usually comes bundled with free software. Consequences are pop-ups, a changed start page, redirected searches and a slow computer.

In Depth

Distinction

Ad-supported programs with consent are legal and not automatically adware. It counts as adware when the advertising is intrusive or appears without clear consent.

Protection

Read installers carefully (“Custom” instead of “Express”), software from official sources, ad blocker, anti-malware.

See also: Freeware, Pop-up, Malware, Shareware