Adware is unwanted software that displays ads to users and collects marketing information about them. It often shows ads and redirects inside the web browser. Advertising can be shown in the interface of free applications - like in Skype, as well as in the installation window of free software. By analyzing the user's search statistics, adware shows an “interesting” advertisement to it.

The difference between adware and a trojan is in its comparative harmlessness. Adware collects information about user behavior on the network, but does not interfere with the operation of the PC and does not steal confidential information (say, bank card data). The main damage is in annoying advertising: pop-up ads, banners, windows that open. Adware monetization is similar to monetization of regular banner advertising when the customer pays for impressions or clicks.

As a rule, an adware program is installed with the formal consent of the user - for example, in a package with a free application in the form of additional software. At the same time, the user does not pay attention to the corresponding “checkmark” and does not know that it can be removed. Or the creators of the software offer to use their product for free, but subject to the display of advertising.

Adware can be picked up on an infected site by clicking on an advertisement that launches a background installation. In such cases, adware is considered spyware because it is installed without user permission and does not have an uninstaller.

Contextual advertising Google and Yandex can be considered a soft version of adware: tools for displaying it are built into the browser, and you can disable them only with the help of third-party software - adblocker.