Adware

Adware (from advertising-supported software) is a type of software whose main purpose is to display advertisements to the user — often intrusive pop-ups, banners, or redirects. Many adware variants also track user activity to better tailor the content they show, which brings them close to spyware.

How adware works

Adware most often reaches a device bundled with free software — it is added to the installer as a pre-checked option that is easy to overlook during setup. Once installed, it may display pop-up windows, inject ads into visited pages, change the browser home page, or redirect searches. Tracking variants gather data about visited sites and interests, frequently using cookies and device identifiers.

In the taxonomy of threats, adware sits close to the PUP (potentially unwanted programs) category. It is not always overtly malicious, but it slows the device, invades privacy, and can be a gateway to more serious attacks when ads lead to data-harvesting sites.

Adware in practice

From a user's perspective, adware is a problem to remove: uninstall suspicious programs, review browser extensions, and run an anti-malware scan. For site owners, the risk is that malicious ad scripts (so-called malvertising) reach a site through infected plugins or a compromised hosting account — which is why up-to-date software, strong passwords, and file-integrity monitoring on the server matter. Protection is further strengthened by mechanisms that separate human traffic from automated traffic, such as CAPTCHA, along with regular CMS and plugin updates and periodic scans of site files for unauthorized changes.