Threats and prevention

The essentials

Malware (malicious software) is software designed to damage, disrupt or gain unauthorised access to computers. Networks also face attacks that overload services or secretly capture data. Knowing how each threat spreads helps in preventing it.

Key points

• Virus: malicious code that attaches itself to a host program or file and spreads when the infected file is run or shared. It needs a host and usually user action.
• Worm: a standalone program that copies itself and spreads across networks automatically, without needing a host file or user action. It can use up network bandwidth.
• Trojan horse: malware disguised as useful or harmless software. It does not replicate itself but can open a backdoor, steal data or damage files once installed.
• Spyware: secretly records user activity and sends it to someone else. Ransomware: locks or encrypts files and demands payment.
• Spam: unwanted bulk messages, usually email, often advertisements or scams.
• Adware: software that displays unwanted advertisements, often bundled with free software.
• Denial of Service (DoS): flooding a server or network with so many requests that genuine users cannot use it. Distributed DoS (DDoS): the attack comes from many compromised computers (a botnet) at once.
• Snooping: secret capture and analysis of network traffic, often with packet-capturing tools.
• Eavesdropping: unauthorised real-time interception of a private communication, such as a phone call or chat.
• Prevention: install and update antivirus software; keep the operating system and applications updated; use a firewall; avoid opening unknown attachments and links; download software only from trusted sources; use strong passwords; take regular backups; use encrypted connections.

Common mistakes

• Calling a Trojan a self-replicating program; replication is a feature of viruses and worms.
• Thinking DoS steals data; its aim is to make a service unavailable.