Malware is software written with malicious code, intended to cause harm to an infected machine. Here’s all you need to know about the different types of malware that are out there.

Malware can have a number of intended effects depending on what type it is, like crippling the system’s operation, allowing cybercriminals to gain access to personal information to defraud or blackmail, spying on the user, or locking the user out of their system’s files. Cybercriminals deliberately code malware to make it as stealthy as possible, in order to keep it undetected from the user for as long as possible. While malware can be an inconvenience for home users, its effects can be devastating on businesses. While the term was first coined in 1990, the history of malware goes back decades, commonly referred to as computer viruses. Nowadays, there are so many malicious pieces of software out there.

Viruses
As we mentioned above, viruses have been around virtually as long as computers have; John von Neumann first wrote about self-replicating computer programs in 1949. The first examples of what we would recognised as viruses emerged in the 1970s. Viruses are categorised as possessing an urge to reproduce, distributing copies of itself to any system it can find. Viruses are also covert, requiring anti-virus software to detect, and hiding and operating in secrecy – which is what makes them so deadly. Viruses hide within files and affect the host when those files are run. Many viruses are hidden in simple executable files like .exe, but any file that Windows can call for execution could be at risk, including script and batch files. Viruses can also infect the operating system so that it remains in operation from the moment the machine is started up, to the moment it is shut down. Some infamous viruses that have plagued users over the years include RavMonE.exe, Brain, the Concept virus and the Chernobyl virus.

Worms
Worms, like viruses, are an infectious form of malware, and rather than adding themselves to existing files, they are carried in their own container. They typically begin by targeting the OS files, until all the files are gone. Because worms utilise large amounts of memory, infected systems can typically become overloaded and stop responding. Worms are different from viruses because they operate alone, and don’t need a host computer. They are typically spread via peer-to-peer file sharing networks, email attachments or malicious links on dodgy websites. Examples of worms include Mylife, Morris, Blaster and Sasser.

Trojan Horses
Like a standard virus, a Trojan horse – or simply Trojan – is a type of malware that is frequently disguised as legit software. Once the user has been tricked into executing a torjan, cyber-criminals will be able to access their system, allowing them to spy. Actions taken can include deleting, modifying or copying data, or disrupting the performance of a machine. As you can imagine, Trojans are classified as one of the more dangerous types of malware that can infect a system. Zeus, Magic Lantern, FinFisher and WARRIOR PRIDE are examples of Torjan horses, and Shedun has targeted Android devices too.

Ransomware
This is another particularly vicious type of malware, and works by blocking access to the user’s data by encrypting it, and demanding a fee for the encryption key; only by paying the ransom will the user be able to access their data again. Ransomware has been around since the 1980s, but has gained notoriety in the age of digital currency. What’s worse, a newer type of ransomware known as doxware blackmails the user with their personal data, threatening to release it to the public; this can be a particular worry for businesses. CryptoLocker is perhaps the most well-known ransomware threat, and the WannaCry attack in 2017 that affected the NHS gained worldwide attention. Sony Pictures was also hit by a doxware attack in late 2014.