# Cyber Security for Beginners ~ 1.6 Virus and Malware
Malware, short for malicious software, is a broad category that includes various types of harmful software designed to compromise or damage computer systems. Among the most well-known varieties are viruses, worms, and trojans.
**Viruses** attach themselves to a clean file and spread throughout a computer system, corrupting or deleting files along the way. They typically activate when users unknowingly execute the infected file.
**Worms** are standalone malware that replicate themselves to spread to other computers, often exploiting network vulnerabilities. Unlike viruses, they do not require human intervention to propagate — making them particularly dangerous.
**Trojans** masquerade as legitimate software, tricking users into installing them. Once activated, trojans can create backdoors for attackers to gain unauthorised access to systems, steal data, or conduct other malicious activities.
Understanding the differences between these types of malware is the first step in recognising and defending against them.