Malware is designed to disrupt computer operation, gather sensitive information, or gain unauthorized access to a computer systems. While it is sometimes software, it can also be hidden script or code on a webpage, or it can be installed through a drive-by download (a rogue app installs itsself during the installation of another program.) Malware includes computer viruses, ransomware, worms, Trojan horses, spyware, rogue exploits, droppers, backdoors, adware, most rootkits, and other malicious programs.
Spyware is a type of software that is installed on your computer to watch and record your activity. Some types of spyware record your keystrokes and information that you type into websites or other programs and then use that information for targeted advertising or identity theft. These programs can be installed on your computer in many ways but often they are hidden inside of software such as free games, updates to Java or Flash Player, illegal music or video downloads, fake antivirus programs, utilities like registry cleaners and programs that claim they will make your computer run faster.
Here are some signs that your computer might be infected with malware:
• You see new toolbars, links, or favorite places that you did not intentionally add to your web browser.
• You type the address of a specific website, the website opens, but the http address is slightly different or you are instead taken to a completely different website.
• Your home page, search engine or mouse pointer has unexpectedly changed.
• You get pop-up ads, particularly for Viagra, or other medications - possibly even when your computer is not connected to the Internet.
• The computer is running slower that usual. Please note that not all computer performance problems are caused by malware. However, malware can cause a noticeable change in computer speed since malware programs run in the background and can take a great deal of memory as they access the internet as a background process and monopolize the processor.
• Sometimes an infected computer will not show any symptoms, even if malware or a rootkit is running. To help protect your privacy and your computer, we recommend that you run an antivirus program andan anti-malware program at all times. If you have the option in your anti-malware program to switch on "search for rootkits," make sure it is enabled.
• If you see a pop-up window disguised as a "official" system notification that claims your computer is infected with malware - do not click on it. If you do, it will usually install more malware and begin to prompt you with ads to remove it by purchasing a fake antivirus program. Literally, in seconds, the scam antivirus program will have purportedly scanned your hard drive and display a report of multiple infections. These fake antivirus programs look convincing because they have the look and feel of the respective operating system.
In fact, if you have never seen how your computer would actually report malware if it did find any, it is worth going to the EICAR (European Institute for Computer Antivirus Research) website to test your current anti-virus software and see what it would look like if your computer were actually infected. This test can be run on any device, including smartphones. Just follow the simple directions on their page at http://www.eicar.org/85-0-Download.html
This linked pdf has dozens of samples of fake error pages one might see, all used to trick the user into clicking on a link that will further infect a computer. The most common fakes claim that: the system is locked; the firewall is not working or has found an infection; and an update of some kind is necessary. The safest solution is to close (or force quit) any web browser when the page is unresponsive. In OS X, click the apple icon in the upper left of the screen and choose Force Quit, then pick the web browser and click the Force Quit button; the keyboard equivalent to open Force Quit is Command+Option+Esc. In Windows, right click the taskbar and choose Start Task Manager, click the Applicaions tab, click on the web browser, then click End Task; the keyboard equivalent to open Task Manager is Ctrl+Shift+Esc.