Difference Between Virus and Trojan

Virus vs Trojan

The term virus has become a term commonly used to describe any unwanted software that gains entry to computers without the user knowing. But a software virus is a specific type of malware that simulates the behavior of the real world virus. It manages to move from one computer to another by attaching to a host file that is oftentimes an executable. A trojan, on the other hand, is simply a piece of malicious code that is disguised as a safe program or more commonly as a game to entice users to execute the code. Trojans do not have the mechanisms needed to propagate or replicate themselves and rely on the user execute their code.

These two types of malware can be easily distinguished by the different methods of propagation. As stated above, a virus uses another executable as a host file. Whenever the file that is infected is run or accessed, the virus is able to run its code and search for other files that it can infect. Trojans, just like their namesake, are passive. They cannot do anything unless the user copies them to the hard drive

Coding a virus can be hard work since you would need to program the mechanisms for the virus to attach itself to another file without rendering it unusable. Trojans are much simpler; a batch file that deletes files in your hard drive without prompt then renamed into some game is already a Trojan. When the user runs it expecting a game, he gets a nasty surprise as the Trojan starts deleting all his files.

The behavior of a virus as it finds host and attaches a copy of itself into new hosts have a general pattern that can be detected by advanced heuristics in an antivirus program. This allows users to detect suspicious activity even when the virus isn’t known to the AV makers yet. But trojans do not share these mechanisms and are therefore harder to detect with antivirus programs until AV makers have identified them as trojans.

Summary:
1. Virus spread themselves across computers by infecting other programs while trojans rely on the users to download or copy them.
2. Virus are complex programs that can hide themselves in other programs while trojans are very simplistic and only uses an enticing file name to disguise itself.
3. Virus can be detected in advance by heuristics due to its behavior while trojans can easily pass through since it does not exhibit any suspicious behavior.

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