Cyber security · GCSE Computer Science

Malware

Malware is malicious software. A virus attaches itself to files and spreads when they are shared. A worm spreads by itself across networks. A trojan pretends to be useful software.
Spyware secretly records what a user does, such as the passwords they type. Ransomware encrypts a victim's files and demands payment to unlock them.

Social engineering tricks people into giving away information or access. People are often the weakest point in a system.
Phishing: fake emails or messages that look genuine, asking you to click a link or enter your details. Blagging (pretexting): making up a story to persuade someone to hand over information. Shouldering (shoulder surfing): watching someone type a PIN or password. Pharming: redirecting users to a fake website.

A brute-force attack tries every possible password until one works. A denial of service (DoS) attack floods a server with requests so it can't respond. SQL injection types SQL code into an input box to read or change a database. Data interception captures data as it travels across a network.
Other risks: weak or default passwords, wrongly set access rights, removable media (such as USB sticks carrying malware) and unpatched (out-of-date) software.

Strong passwords, limits on login attempts, CAPTCHA, two-factor authentication and biometrics (such as fingerprints) protect accounts.
Anti-malware software, firewalls (which block unauthorised network traffic), automatic updates, encryption (so intercepted data can't be read), user access levels, physical security and backups protect systems and data.
Penetration testing: authorised experts attack a system to find its weaknesses before criminals do. Input validation helps to stop SQL injection. Staff training helps people spot social engineering.

Encryption scrambles data with a key, so only someone with the key can read it.
A simple example is the Caesar cipher, which shifts each letter a set number of places along the alphabet: with a shift of 3, CAT becomes FDW. It is easy to crack, so real systems use much stronger methods.

Malware: Malicious software, such as viruses, worms, trojans and spyware.
Trojan: Malware that pretends to be useful software.
Spyware: Malware that secretly records what a user does.
Phishing: Fake messages designed to trick people into giving away their details.
Blagging: Making up a story to persuade someone to hand over information or access.
Brute-force attack: Trying every possible password until one works.
Denial of service: Flooding a server with requests so it can't respond to real users.
SQL injection: Typing SQL code into an input box to access or change a database.
Firewall: Hardware or software that blocks unauthorised network traffic.
Penetration testing: Authorised attacks on a system to find its weaknesses.