From creating popups to redirecting your searches and collecting information about your browsing history, adware is an invasion of privacy. But how does software like this get on your computer?

Popups saying that your computer is infected ,ore often than not come with a message for you to “Click Here.” However, any virus alert that isn’t from the program you recognize could be an attempt to install adware or malicious software to your computer. Even worse, the developers of that adware could ultimately charge you to remove it from your system.

Outdated software that may contain vulnerabilities is among the most common ways for adware to find itself on your system. Java, a program that allows applets to load in other programs and your browser, is perhaps the most notable culprit. If your installation of Java is outdated, it may provide a backdoor to your computer, which adware developers will use to install programs you don’t want on your system. This is one reason, aside from improved features and performance, that you’ll want to download new updates as soon as they become available.

AdWare can come with legitimate programs. Often times, developers of free programs will bundle other software, typically in the form of browser add-ons, with the software you’re trying to download. If you look closely, you’ll see that many programs ask whether you want to make changes, such as your browser’s home page or search engine, or whether you want to add bundled software with the program you’re trying to add. However, you can typically select “Cancel” or uncheck these options.

Email attachments can also contain adware and even more malicious software, even if they come from someone in your address book. If someone you know has had their email hacked, everyone in their address list could receive seemingly-legitimate messages. Always beware attachments in emails, especially if they come in the format of ZIP, which requires you to extract them, or EXE, a program file. Run an anti-virus program that will scan any incoming files and warn you when a file is malicious.

Much adware is easy to remove from the control panel or by disabling plugins and toolbars from your browser. However, you may have difficulty removing some adware if it’s installed in multiple browsers. Increasing security settings of your computer so that software installation requires your permission can help to deter adware from becoming installed on your PC.