Trojans can look like just about anything, from free software and music, to browser advertisements to seemingly legitimate apps. Any number of unwise user behaviors can lead to a Trojan infection. Here are a few examples:
- Downloading cracked applications. Promises of an illegal free copy of a piece of software can be enticing, but the cracked software or activation key generator may conceal a Trojan attack.
- Downloading unknown free programs. What looks like a free game or screensaver could really be a Trojan, especially if you find it on an untrustworthy site.
- Opening infected attachments. You get a strange email with what looks like an important attachment, like an invoice or a delivery receipt, but it launches a Trojan when you click on it.
- Visiting shady websites. Some sites only need a moment to infect your computer. Others use tricks like pretending to stream a popular movie, but only if you download a certain video codec, which is really a Trojan.
- Any other social engineering that disguises itself by taking advantage of the latest trends. For example, in December 2017, an extensive installed base of Intel processors was discovered to be vulnerable to attack due to hardware issues. Hackers leveraged the ensuing panic by faking a patch called Smoke Loader, which installed a Trojan.