Adware shows you ads you did not ask for. Some of it is legitimate, bundled with free software and disclosed in the installer. Most of it is not. The bad kind hijacks your browser, changes your homepage, injects pop-ups into pages you visit, and tracks what you search for. It slows your machine and sells your browsing habits to advertisers you never heard of.

The line between adware and malware has blurred. Adware that redirects searches and refuses to uninstall behaves like malware. Some adware bundles spyware that logs keystrokes or steals credentials. The 2017 Fireball operation infected 250 million devices by bundling adware with free downloads. Most victims never knew. Removal is often tedious. The software may install multiple components, hide in scheduled tasks, and reinstall itself if you remove only part of it. Safe mode, a full scan, and manual cleanup of browser extensions usually does the job. Prevention is simpler. Read installer screens carefully and decline bundled offers. Download from official sources. Keep a browser extension that blocks known ad networks.

Signs of adware infection

• Pop-ups appear when no browser is open
• Homepage or default search engine changes without your input
• New toolbars appear in the browser
• The machine runs noticeably slower

Adware rarely destroys data. It just makes the machine unpleasant to use and quietly monetizes your attention.