Difference Between Worms, Trojans and Viruses

Worms, trojans and viruses are subcategories of malware.

Malware, meaning malicious software, is specifically designed to damage or steal private information from computer data, networks and hosts. However, malware cannot damage hardware on your computer. Worms, trojans and viruses are specific classes of malware.

Worms

Worms can replicate copies of themselves. This malware does not require a host program or human action to carry out its intentions. The software infects by exploiting vulnerabilities in systems or by tricking a user into executing the worm. From that point, the worm travels unaided by the file-transport or information-transport features of a system.

Trojans

Named after the wooden horse used by the ancient Greeks to infiltrate Troy, this type of malware infects by looking like a legitimate program. Users are tricked into loading and executing the software. Trojans can cause a variety of problems from randomly popping up windows to deleting files, stealing data and spreading viruses.

Viruses

Like worms, viruses can make copies of themselves. However, a virus has to insert itself into and become a part of another program. Viruses spread from one computer to another, infecting each system as they travel. They can damage data and software and cause denial-of-service conditions. Viruses may exist dormant in systems until the program to which they are attached is executed. Sometimes the viruses can destroy the host program entirely.

References

• Cisco: What Is the Difference: Viruses, Worms, Trojans, and Bots?