What is a threat?

A threat is the ability of an entity to gain access to or interfere with the usual planned activities of an information network.

What is an APT?

An advanced persistent threat (APT) is a stealthy computer network threat actor, typically a nation state or state-sponsored group, which gains unauthorized access to a computer network and remains undetected for an extended period. In recent times, the term may also refer to non-state sponsored groups conducting large-scale targeted intrusions for specific goals.

What is phishing?

Phishing is the fraudulent attempt to obtain sensitive information such as usernames, passwords and credit card details by disguising oneself as a trustworthy entity in an electronic communication. Typically carried out by email spoofing or instant messaging, it often directs users to enter personal information at a fake website which matches the look and feel of the legitimate site.

Phishing is an example of social engineering techniques being used to deceive users. Users are often lured by communications purporting to be from trusted parties such as social web sites, auction sites, banks, online payment processors or IT administrators.

What is malware?

Malware (a portmanteau for malicious software) is any software intentionally designed to cause damage to a computer, server, client or computer network (in contrast, software that causes unintentional harm due to some deficiency is typically described as a software bug). A wide variety of malware types exist, including computer viruses, worms, Trojan horses, ransomware, spyware, adware, rogue software and scareware.

Programs are also considered malware if they secretly act against the interests of the computer user. For example, at one point, Sony music compact discs silently installed a rootkit on purchasers' computers with the intention of preventing illicit copying, but which also reported on users' listening habits, and unintentionally created extra security vulnerabilities.

A range of antivirus software, firewalls and other strategies are used to help protect against the introduction of malware, to help detect it if it is already present and to recover from malware-associated malicious activity and attacks.

What is a botnet?

A botnet is a number of Internet-connected devices, each of which is running one or more bots. Botnets can be used to perform Distributed Denial-of-Service (DDoS) attacks, steal data, send spam and allows the attacker to access the device and its connection. The owner can control the botnet using command and control (C&C) software. The word "botnet" is a portmanteau of the words "robot" and "network". The term is usually used with a negative or malicious connotation.

What is a DDoS-attack?

A distributed denial-of-service (DDoS) attack occurs when multiple systems flood the bandwidth or resources of a targeted system, usually one or more web servers. Such an attack is often the result of multiple compromised systems (for example, a botnet) flooding the targeted system with traffic. A botnet is a network of zombie computers programmed to receive commands without the owners' knowledge. When a server is overloaded with connections, new connections can no longer be accepted. The major advantages to an attacker of using a distributed denial-of-service attack are that multiple machines can generate more attack traffic than one machine, multiple attack machines are harder to turn off than one attack machine and that the behavior of each attack machine can be stealthier, making it harder to track and shut down. These attacker advantages cause challenges for defense mechanisms. For example, merely purchasing more incoming bandwidth than the current volume of the attack might not help, because the attacker might be able to simply add more attack machines. This, ultimately, will end up completely crashing a website for periods of time.

What is ransomware?

Ransomware is a type of malware from cryptovirology that threatens to publish the victim's data, or perpetually block access to it, unless a ransom is paid. While some simple ransomware may lock the system in a way which is not difficult for a knowledgeable person to reverse, more advanced malware uses a technique called cryptoviral extortion, in which it encrypts the victim's files, making them inaccessible, and demands a ransom payment to decrypt them. In a properly implemented cryptoviral extortion attack, recovering the files without the decryption key is an intractable problem – and difficult to trace digital currencies such as Ukash or Bitcoin and other cryptocurrency are used for the ransoms, making tracing and prosecuting the perpetrators difficult.
Ransomware attacks are typically carried out using a Trojan that is disguised as a legitimate file that the user is tricked into downloading or opening when it arrives as an email attachment. However, one high-profile example, the "WannaCry worm", travelled automatically between computers without user interaction.