A keylogger records every keystroke a user makes and transmits the data to the attacker. This allows the attacker to capture passwords, banking details, and private messages. A worm self-replicates across networks. Ransomware encrypts files and demands payment. Adware displays unwanted adverts.

A worm is self-replicating malware that spreads independently across a network without needing to attach itself to a host file. It exploits network connections to copy itself to other devices. A Trojan disguises itself as legitimate software. Ransomware encrypts files for payment. A man-in-the-middle attack intercepts network traffic.

Phishing uses fraudulent emails or messages designed to look legitimate, directing victims to fake websites where they enter credentials that are then stolen. Brute force systematically tries passwords. SQL injection targets database queries. A DoS attack floods a server with requests to make it unavailable.

This is social engineering through pretexting - the attacker creates a fabricated scenario (pretending to be IT support) to gain trust and extract information. While vishing is voice-based phishing, the defining feature here is the manipulation using a false identity and context, which is the essence of social engineering and pretexting specifically.

SQL injection inserts malicious SQL code into an input field. The injected code manipulates the database query. In this example, the semicolon ends the original query, DROP TABLE users deletes the users table, and -- comments out the rest of the original query. This can corrupt, delete or extract data from the database.

A DDoS (Distributed Denial of Service) attack uses many different machines - often thousands of compromised devices in a botnet - to flood the target simultaneously. Because requests come from many IP addresses, blocking them is far more difficult than blocking a single source. A DoS attack originates from one machine, making it easier to identify and block.

Symmetric encryption uses one shared key for both encryption and decryption. Both parties must know the secret key. While this is fast and efficient, the challenge is securely sharing the key. Asymmetric (public key) encryption uses a matched key pair - a public key to encrypt and a private key to decrypt. Hashing is a one-way process and is not reversible.

Port 23 is the default port for Telnet, an unencrypted remote access protocol. Blocking it is common security practice because Telnet transmits data including passwords in plain text. SSH (port 22) is the secure replacement. HTTPS uses port 443. FTP uses ports 20 and 21.

User access levels (access controls / permissions) restrict what each account can read, write, or modify. Applying the principle of least privilege, each user is given only the access they need for their role. 2FA verifies identity. Penetration testing finds vulnerabilities. An AUP is a document of rules, not a technical control.

Defence in depth (also called layered security) is the strategy of combining multiple, independent security measures so that if one layer is bypassed, others still protect the system. No single control is relied upon alone. This is contrasted with a single-point solution where compromising one control breaks all security.