Types of cyber attack

Denial of service/distributed denial of service attack

A denial of service (DoS) attack is a cyber incident that involves a deliberate attempt to disrupt a computer system or network that is connected to the internet. DoS attacks often target specific organisations and may be only one part of a wider attack on an organisation.

Distributed denial of service (DDoS) attacks are a more sophisticated DoS attack. A DDoS attack uses a compromised network of computers (so-called botnets), often without the owners’ knowledge of the owners of the compromised computers, to launch the attack.

Although techniques and motives may vary, DoS and DDoS attacks are generally intended to temporarily or indefinitely interrupt or suspend the services of an organisation connected to the internet.

Spear phishing

Spear phishing describes efforts to acquire sensitive or confidential information about individuals or organisations through fraudulent electronic communications such as fake emails or links to fake websites.

Whaling refers to spear phishing attacks specifically targeted at senior executives or other high-profile targets within a business.

Viruses, worms and Trojan horses

Malicious software (so-called malware) used to perpetrate cyber security incidents takes many forms, most notably viruses, worms and Trojan horses.

Viruses are malware that, when executed, replicate by "infecting" other computer programs, systems or files. As well as replicating, viruses often corrupt or steal data, displaying political messages or logging keystrokes. These other functions are known as the virus "payload".

Worms are stand-alone malware programs that replicate to spread to other computers. Unlike viruses, they do not need to attach themselves to existing programs to replicate. As with viruses, worms can carry a harmful payload (although even those that do not can cause disruption through increased network traffic and other unintended consequences). A common payload for worms is to install a "back-door" to enable a computer to be controlled by an external third party, for example, for use as part of a botnet (see denial of service/distributed denial of service attacks, above).

A Trojan Horse or Trojan program is a non-self-replicating malware program that hacks into a computer system or network by appearing to perform a useful function. Instead they deliver a harmful payload. As with worms, the payload will often include a backdoor that gives unauthorised access to the network or system. Trojans do not try to insert themselves into other files, like viruses, but they can steal information and harm host computer systems and networks.