Trojans and spyware are two common forms of malware that infect computers, but they work differently. Malware is the blanket term that describes all types of malicious software, spyware and Trojans among them. Spyware and Trojans are both designed to infect your system quietly and can be hard to detect, but both compromise the safety of your computer and warrant immediate removal.
Spyware is designed to stay hidden and collect your information in the background. Unlike many other types of malware, you won't see its effects; the longer it goes undetected, the more information it can steal. It can record what keys you type, steal passwords and email addresses and collect entries from your address book like phone numbers, addresses and emails. This information is sent to the creator of the spyware, whether it be a company or an individual.
A Trojan horse -- often shortened to "Trojan" -- is a virus that infects your system by pretending to be something else, much like its name implies. It masquerades as a helpful or harmless program or file, then infects your hard drive when you open it or install the fake program. After that it often takes over and uses your computer to download more malware, most often spyware.
Differences and Dangers
Both spyware and Trojans operate in the background, but Trojans are often the gateway to infections from spyware, downloading it directly to your computer. Trojans can also take control of some of your computer's functions, whereas spyware attempts to make as few changes as possible so it can remain undetected.
Safety and Removing Malware
Installing programs specifically designed to remove malware will remove most spyware and Trojans. Use a program like SuperAntiSpyware, Ad-Aware or Malwarebytes to scan your entire hard drive to remove any traces of infection. After removing all malware from your system, change your passwords and check all your online accounts; if your passwords or other data were stolen, it's imperative to change your login data on all your accounts immediately.
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