Adware

Adware is software that displays advertising on a computer, redirects search results to advertising websites and collects user data for marketing purposes. Adware's purpose is to generate revenue for its developer by serving ads to an internet user while they are surfing the web or during the initial installation process. Its functions may be seen in a variety of ways, from display and banner ads to full-screen ads, videos, pop-ups or other varieties of online and mobile advertising. Adware is mostly used legitimately though can be malicious in nature. Users can often disable the frequency of adware by managing the pop-up controls and preferences within their internet browsers. Adware is a term that originates from "advertising-supported software." 

Adware can track which internet sites a user visits and then present advertisements based on the types of web pages viewed. Adware, while sometimes intrusive and annoying, is usually not a threat to a computer system. It is hardly ever noticed by computer users, rarely making its presence known. It can find its way onto computers via freeware or shareware as a way of generating advertising revenue for software developers. 

Generally speaking, adware generates revenue in two ways: the display of advertising to a user's computer and a per-click payment made if a user clicks on the ad. Most often, adware is bundled within legitimate programs. Adware works with all web browsers. 

When adware use began roughly in 1995, some industry experts considered all adware to be spyware. Later, as the legitimacy of adware grew, it was thought of as merely a "potentially unwanted program." As such, its use proliferated and not too much was done to monitor its legitimacy. It wasn't until the peak adware years of 2005–2008 when adware vendors started to monitor and shut down questionable activities.

Adware is considered by many to be synonymous with "malware," which is malicious software that serves unwanted advertisements to internet users. Some examples include pop-up ads or unclosable windows. Adware can find its way onto computers via infected websites through an unauthorized installation. Adware that tracks a computer user's activities without their consent or knowledge and then reports that data to the software's creator is known as "spyware." Once malicious adware is on a computer it might carry out a variety of unwanted tasks, track a user's location, search activity and web page viewing history, and then sell this information to third parties. Programs are widely available that can detect, prevent and remove adware. Often, they are free or come as part of free antivirus software. Some popular options include Bitdefender Antivirus Free Edition, AVG AntiVirus Free, Spybot – Search & Destroy, Malwarebytes Anti-Malware and Emsisoft Emergency Kit.