Computer virus in the context of Hex dump

Self-replication is any behavior of a dynamical system that yields construction of an identical or similar copy of itself. Biological cells, given suitable environments, reproduce by cell division. During cell division, DNA is replicated and can be transmitted to offspring during reproduction. Biological viruses can replicate, but only by commandeering the reproductive machinery of cells through a process of infection. Harmful prion proteins can replicate by converting normal proteins into rogue forms. Computer viruses reproduce using the hardware and software already present on computers. Self-replication in robotics has been an area of research and a subject of interest in science fiction. Any self-replicating mechanism which does not make a perfect copy (mutation) will experience genetic variation and will create variants of itself. These variants will be subject to natural selection, since some will be better at surviving in their current environment than others and will out-breed them.

Malware (a portmanteau of malicious software) is any software intentionally designed to cause disruption to a computer, server, client, or computer network, leak private information, gain unauthorized access to information or systems, deprive access to information, or which unknowingly interferes with the user's computer security and privacy. Researchers tend to classify malware into one or more sub-types (i.e. computer viruses, worms, Trojan horses, logic bombs, ransomware, spyware, adware, rogue software, wipers and keyloggers).

Malware poses serious problems to individuals and businesses on the Internet. According to Symantec's 2018 Internet Security Threat Report (ISTR), malware variants number has increased to 669,947,865 in 2017, which is twice as many malware variants as in 2016. Cybercrime, which includes malware attacks as well as other crimes committed by computer, was predicted to cost the world economy US$6 trillion in 2021, and is increasing at a rate of 15% per year. Since 2021, malware has been designed to target computer systems that run critical infrastructure such as the electricity distribution network.

A bounty is a payment or reward of money to locate, capture or kill an outlaw or a wanted person. Two modern examples of bounties are the ones placed for the capture of Saddam Hussein and his sons by the United States government and Microsoft's bounty for computer virus creators. Those who make a living by pursuing bounties are known as bounty hunters.

Bounties have also been granted for other actions, such as exports under mercantilism.

A computer worm is a standalone malware computer program that replicates itself in order to spread to other computers. It often uses a computer network to spread itself, relying on security failures on the target computer to access it. It will use this machine as a host to scan and infect other computers. When these new worm-invaded computers are controlled, the worm will continue to scan and infect other computers using these computers as hosts, and this behavior will continue. Computer worms use recursive methods to copy themselves without host programs and distribute themselves based on exploiting the advantages of exponential growth, thus controlling and infecting more and more computers in a short time. Worms almost always cause at least some harm to the network, even if only by consuming bandwidth, whereas viruses almost always corrupt or modify files on a targeted computer.

Many worms are designed only to spread, and do not attempt to change the systems they pass through. However, as the Morris worm and Mydoom showed, even these "payload-free" worms can cause major disruption by increasing network traffic and other unintended effects.

Cyberweapons are commonly defined as malware agents employed for military, paramilitary, or intelligence objectives as part of a cyberattack. This includes computer viruses, trojans, spyware, and worms that can introduce malicious code into existing software, causing a computer to perform actions or processes unintended by its operator.

In computing and telecommunications, the payload is the part of transmitted data that is the actual intended message. Headers and metadata are sent only to enable payload delivery and are considered overhead.

In the context of a computer virus or worm, the payload is the portion of the malware which performs malicious action.

A logic bomb is a piece of code intentionally inserted into a software system that will set off a malicious function when specified conditions are met. For example, a programmer may hide a piece of code that starts deleting files (such as a salary database trigger), should they ever be terminated from the company.

Software that is inherently malicious, such as viruses and worms, often contain logic bombs that execute a certain payload at a pre-defined time or when some other condition is met. This technique can be used by a virus or worm to gain momentum and spread before being noticed. Some viruses attack their host systems on specific dates, such as Friday the 13th or April Fools' Day. Trojans and other computer viruses that activate on certain dates are often called "time bombs".

Rogue security software is a form of malicious software and internet fraud that misleads users into believing there is a virus on their computer and aims to convince them to pay for a fake malware removal tool that actually installs malware on their computer. It is a form of scareware that manipulates users through fear, and a form of ransomware. Rogue security software has been a serious security threat in desktop computing since 2008. An early example that gained infamy was SpySheriff and its clones, such as Nava Shield.

With the rise of cyber-criminals and a black market with thousands of organizations and individuals trading exploits, malware, virtual assets, and credentials, rogue security software has become one of the most lucrative criminal operations.

Shamoon (Persian: شمعون), also known as W32.DistTrack, is a modular computer virus that was discovered in 2012, targeting then-recent 32-bit NT kernel versions of Microsoft Windows. The virus was notable due to the destructive nature of the attack and the cost of recovery. Shamoon can spread from an infected machine to other computers on the network. Once a system is infected, the virus continues to compile a list of files from specific locations on the system, upload them to the attacker, and erase them. Finally the virus overwrites the master boot record of the infected computer, making it unusable.

The virus was used for cyberwarfare against national oil companies including Saudi Arabia's Saudi Aramco and Qatar's RasGas. A group named "Cutting Sword of Justice" claimed responsibility for an attack on 30,000 Saudi Aramco workstations, causing the company to spend more than a week restoring their services. The group later indicated that the Shamoon virus had been used in the attack. Computer systems at RasGas were also knocked offline by an unidentified computer virus, with some security experts attributing the damage to Shamoon. It was later described as the "biggest hack in history".

Antivirus software (abbreviated to AV software), also known as anti-malware, is software intended to prevent, detect, and remove malware.

Antivirus software was originally developed to detect and remove computer viruses, hence the name. However, with the proliferation of other malware, antivirus software started to protect against other computer threats. Some products also include protection from malicious URLs, spam, and phishing.

Leonard Adleman (born December 31, 1945) is an American computer scientist. He is one of the creators of the RSA encryption algorithm, for which he received the 2002 Turing Award. He is also known for the creation of the field of DNA computing and coining the term computer virus.

Brain is the industry standard name for a computer virus that was released in its first form on 19 January 1986, and is considered to be the first computer virus for the IBM Personal Computer (IBM PC) and compatibles.

Malware analysis is the study or process of determining the functionality, origin and potential impact of a given malware sample such as a virus, worm, trojan horse, rootkit, or backdoor. Malware or malicious software is any computer software intended to harm the host operating system or to steal sensitive data from users, organizations or companies. Malware may include software that gathers user information without permission.