Adware is any software application in which advertising banners are displayed while a program is running. The ads are delivered through pop-up windows or bars that appear on the program's user interface. Adware is commonly created for computers, but may also be found on mobile devices.

The justification for adware is that it helps recover programming development costs for the software developer, and reduces or eliminates the cost for the user.

Types of adware

Some legitimate application software is offered as either a free version that is advertising-supported or as a paid version without advertisements. Users would purchase a software license code or a separate piece of software for an ad-free experience. This type of adware gives users the opportunity to access the software without making large payments.

Adware has been criticized because it often includes code that tracks and records users' personal information and internet browsing habits. While this data may be used with the user's consent for displaying customized ads, the software can be classified as spyware if it is done without the user's knowledge and authorization. User data collected in this manner is often sold to third parties. These intrusive practices have prompted an outcry from computer security and privacy advocates, including the Electronic Privacy Information Center.

adware example
Example of adware

Malicious adware or spyware may be bundled in with free software, shareware programs and utilities downloaded from the internet, or surreptitiously installed onto a user's device when the user visits an infected website. Adware is often flagged by antimalware programs as a potentially unwanted program, whether the adware program in question is malicious or not.

Detection and removal tools

A user's device could possibly be infected with malicious adware if there has been a spike in data usage, the appearance of new toolbars on the user's web browser, redirection of the user's internet searches to advertising websites, the appearance of unwanted ads in pop-up windows that cannot be easily closed or if the device runs slowly.

Most endpoint security suites have the ability to scan for and remove adware, spyware and other malware programs. A number of software applications, including Lavasoft's Ad-Aware and Bitdefender's Adware Removal Tool, are available for free to help computer users search for and remove suspected spyware programs.


To avoid adware infections, users should be discerning about the types of software they download online, should read end-user license agreements before downloading free software to find out if the software authors will conduct information gathering on their devices, should use a pop-up ad blocker to prevent unexpected windows from opening and should avoid clicking on ads if they are not being displayed on a trusted site.

This was last updated in April 2017

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