Describe the main types of malware that a SOC analyst should be familiar with, including viruses, worms, trojans, ransomware, and spyware. How does each one behave differently?

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Malware is a broad term for any software intentionally designed to cause damage, steal data, or gain unauthorized access to systems. As a SOC analyst, understanding the different categories of malware helps you quickly assess the severity of an alert and determine the right response steps. Here are the main types you will encounter.

A virus is malware that attaches itself to a legitimate program or file. It requires human action to spread, such as opening an infected email attachment or running a compromised executable. Once activated, a virus can corrupt files, slow down systems, or open backdoors. The key characteristic is that viruses do not spread on their own; they need a host file and user interaction.

A worm is similar to a virus but with one critical difference: it can spread automatically across networks without any user interaction. Worms exploit vulnerabilities in operating systems or network services to propagate from machine to machine. The WannaCry attack in 2017 is a famous example where a worm spread rapidly across organizations by exploiting a Windows SMB vulnerability. Worms can consume network bandwidth and system resources even before delivering their payload.

A trojan, named after the Trojan Horse from Greek mythology, disguises itself as legitimate software. A user might download what appears to be a useful application, but hidden inside is malicious code. Trojans do not replicate themselves. Instead, they rely on social engineering to trick users into installing them. Once active, trojans can create backdoors, steal credentials, or download additional malware.

Ransomware encrypts a victim's files and demands payment in exchange for the decryption key. This type of malware has become one of the most damaging threats to organizations. Ransomware often arrives through phishing emails or by exploiting unpatched vulnerabilities. SOC analysts need to recognize the signs of ransomware quickly, such as mass file encryption events, ransom notes appearing on desktops, and unusual file extension changes.

Spyware operates silently in the background, collecting information about a user's activities without their knowledge. It can capture keystrokes, take screenshots, record browsing history, and harvest credentials. Spyware is often bundled with free software or delivered through malicious advertisements.

Understanding these categories helps you prioritize alerts. A ransomware detection, for example, demands immediate containment, while spyware may require a thorough investigation to determine what data was exfiltrated.