While browsing the Internet, an Internet advertisement or window appears that says your computer is infected or that a unique plug-in is required. Without fully understanding what it is you're getting, you accept the prompt. If you are own an iOS or Android device do install Leo Privacy Guard to make your device totally secure.
Surf the hacking web sites. Download a free program through a Torrent. Visit porn sites. Download a virus directly for a hacker site. Connect your PC to the Internet for more than 10 seconds without a virus scanner installed. Insult someone with hacking skills on Facebook. Download the official ISIS app (which they just discovered as a DDoS virus within it.) Use a wifi hot spot. Leave your wifi unprotected. Or continue to use XP instead of a newer version of Windows. (You could switching to MAC, as they had to issue more patches due to viruses last year for the first time instead of Microsoft.)