Malware (Viruses, Trojans, Worms)

What is Malware?

Malware (short for Malicious Software) is any software intentionally designed to cause damage to a computer, server, client, or computer network, or to steal private information.

1. Computer Virus

• How it works: A virus is a piece of code that attaches itself to a legitimate, clean program or file (like an .exe file or Word document).
• Propagation: It requires human action to spread. If you never open the infected file, the virus cannot run or spread to other files.
• Goal: Corrupt files, delete data, or destroy the operating system.

2. Worm

• How it works: A worm is a standalone malicious program. It does NOT need to attach itself to a host file.
• Propagation: It spreads automatically over a computer network by exploiting security vulnerabilities. It does not require human interaction. Once one computer on a network is infected, the worm scans for other connected computers and copies itself over.
• Goal: Consume network bandwidth (causing slow internet) or drop other malware.

3. Trojan Horse

• How it works: Named after the Greek wooden horse, a Trojan disguises itself as a legitimate, useful, or harmless program (like a free game or a software crack).
• Propagation: Users are tricked into downloading and installing it themselves.
• Goal: Once inside, it creates a 'backdoor' for hackers to secretly access and control the computer, steal passwords, or spy on the user. Trojans do not replicate themselves.

4. Ransomware

• How it works: It is a type of malware that rapidly encrypts all the user's personal files, making them completely inaccessible.
• Goal: Extortion. It displays a message demanding payment (a ransom, usually in Bitcoin) in exchange for the decryption key to unlock the files.

5. Spyware & Keyloggers

• Spyware: Secretly installs itself and spies on the user's internet activity, showing them unwanted ads (Adware) or stealing data.
• Keylogger: A specific type of spyware that secretly records every single keystroke the user types on their keyboard, specifically to steal passwords and credit card numbers.