Pop-up ads often appear due to installed adware - software used to generate revenue for developers by feeding regular users with unwanted ads. Rather than closing the ad, the click performs other unwanted actions. People are often tricked into clicking these ads when a fake 'close button' is applied to them. There is a high probability that any downloaded or installed PUAs will be malicious. To achieve this, however, they must first be clicked. Rogue pop-up ads sometimes run scripts that download and install PUAs. These sites often state that the visitor's computer is infected with viruses that must be removed immediately using various potentially unwanted apps (PUAs). If clicked, pop-up ads open dubious websites - for example, deceptive web pages that trick people into downloading unwanted applications. However they are displayed, pop-ups are annoying and cannot be trusted. Their presence is due to installed adware or visited websites that use rogue advertising networks. Typically, they appear in the foreground of a visited website and thus often conceal underlying content. POP-UP ads (or simply 'pop-ups) are advertisements that usually appear in smaller windows.
