Adware is software that displays unwanted advertisements, redirects searches or injects ads into web pages to earn money for its developers, often while tracking the user’s browsing.
How adware works
Adware usually reaches devices bundled with free programs, through fake browser extensions or as mobile apps that look useful – a flashlight, a game or a photo filter. Once installed, it may:
- show pop-ups, full-screen ads or notifications, even when the app is not in use;
- change the browser’s homepage and default search engine;
- inject ads into websites or replace existing ones;
- collect browsing history and device data for ad targeting.
Mobile adware frequently hides its icon after installation, so users cannot easily find and remove it. Security vendors classify milder adware as a potentially unwanted program and more aggressive variants as malware.
Why adware matters
Beyond annoyance, adware weakens security. In 2015 Lenovo laptops shipped with Superfish, adware that installed its own root certificate to inject ads into HTTPS pages – effectively a man-in-the-middle attack that exposed users to interception. In 2017 Check Point reported Fireball, browser-hijacking adware from a Chinese marketing company that infected an estimated 250 million computers and could download arbitrary code. Ads served by adware can also lead to scams and malvertising.
How to protect against adware
- Download software from official sources and choose “custom install” to decline bundled offers.
- Review browser extensions and mobile apps regularly and remove ones you do not recognise.
- Be suspicious of apps that request admin or overlay permissions they do not need.
- Use reputable security software and an ad blocker to reduce exposure.
