Everyone hates a pop-up; it dominates your screen, usually with something unsavory, and indicates the potential of a malware infection. While any website that promises "free" files, apps or other material may include pop-up ads or malware that causes them, they are not exclusive to iffy websites. Even legitimate websites, such as social networking sites and search engines, may serve unwanted pop-ups.

Pop-ups in the Browser

If you're receiving pop-up ads when you visit certain websites, the ads are likely embedded on the website. These ads tend to open up in the background so that you don't notice them until you've closed your main browser window. While all major browsers include the option to block pop-ups, these settings don't catch every ad. The best way to avoid these sorts of pop-ups is to install an ad-block extension in your browser. Both Google Chrome and Mozilla Firefox have prominent ad-block applications available for free download.

Pop-ups on Your Computer

If ads appear in the form of pop-ups when your browser is not in use, a virus or some other malware on your system prompts those ads. You may also notice that your system slows down or uses more resources than necessary when nothing is running; this also indicates that you're infected with malware. These sort of infections must be handled with anti-malware programs, though once you're infected it can be difficult to remove malware from your system.

Anti-malware Programs

Anti-malware programs come in both free and commercial varieties, depending on what sort of protection you need. If you already have an anti-virus program on your computer, Lincoln Spector of PC World recommends using a new one for the process of removing malware, since your original protection failed to catch the infection. His advice is to use either Bitdefender or the ESET Online Scanner. Malwarebytes Anti-Malware is another popular anti-malware program that offers a free version. If you didn't have any sort of anti-virus or malware protection, Windows Security Essentials is a free security tool for once you've removed your current malware.

Removing Established Infections

An established malware infection is hard to remove; most malware attempts to block legitimate processes and programs from doing so. Malware also usually adds itself to your list of start-up processes, making it hard to remove before it's running. Spector recommends booting your computer into "Safe Mode with Networking," so you can get online with Internet Explorer and run either Bitdefender or the ESET Online Scanner. Both tools are browser-based, kept up-to-date with the latest malware definitions and allow you to run a fresh anti-malware scan without installing more software on your computer.