No doubt you are probably asking this question because your computer is infected and you are wondering how. There are many ways how malware can get on your computer, but here I will list the five most common ways how you could get infected.
Number 1: Drive-By Websites
This is the most common way you could get infected without you knowing about it. Basically a malicious website, when you visit it (or sometimes you could get infected without you even visiting the website), will automatically drop some malware on your computer. This could happen anywhere: on Facebook, Google, or basically any website. Even some reputable websites could get comprised and start handing out malware. Just be careful of what links you click on.
Number 2: Bundled Software
Many software installers offer an optional component to install. This could be in the form of a toolbar, or an application. Many times this is usually malware or junk software, and will hog up your system resources. The trick is to carefully read the steps in a software installer, and look out for any bundled software that the installer is trying to install. Most of the time, a simple “Decline” will do the trick, however with certain software even clicking “Decline” will still install the supposedly optional software to your computer.
Number 3: Malware Droppers
Once you get infected, malware can install even more malware to your computer. Malware could run in the background without you even knowing, and download more malware to your computer. Often they will disable your firewall and anti-virus software to prevent the malware from being blocked.
Number 4: Removable Media
Viruses can “hop” from one computer to another over a flash drive or removable media. Be sure to scan all removable drives, especially if it comes from an untrusted source. Many times a computer virus will write itself to the “autorun” of the drive, so if autorun is enabled on the computer (it probably is) the virus will automatically run when you put the drive in. Be sure to have a real-time anti-virus to stop the virus in its tracks or just disable autorun.
Number 5: File Sharing
Be wary of file sharing over the internet. Many emails often contain attachments, and these attachments could be malicious. Only open attachments from trusted sources, as your friend could be unknowingly passing along a computer virus to you. With other file sharing services such as torrents, be sure to scan all downloaded files before executing them. Torrents and other file sharing services are often very unpredictable so you don’t know which file contains a virus or not. You just have to be careful on what you choose to download.