Malware is typically used as a catch-all term to refer to any software designed to cause damage to a single computer, server, or computer network, whether it's a virus, spyware, etc. The most common types are listed below
Adware
Adware or advertising-supported software is any software package which automatically plays, displays, or downloads advertisements to a computer after the software is installed on it or while the application is being used. Some types of adware are also spyware and can be classified as privacy-invasive software.
More annoying than malicious.
Botnets
Botnet is a jargon term for a collection of software robots, or bots, that run autonomously and automatically. The term is often associated with malicious software but it can also refer to the network of computers using distributed computing software.
Your computer could be sending spam or be partaking in a DDOS attack as part of botnet network.
Key loggers
Keystroke logging (often called key logging) is a method of capturing and recording user keystrokes. It enables passwords and other Personally Identifiable Information typed into a computer to be used for fraudulent purposes.
Your personal information is at risk.
PUA
PUA is a term used to describe applications that, while not malicious, are generally considered unsuitable for business networks. The major PUA classifications are adware, dialler, non-malicious spyware, remote administration tool and hacking tool. However, certain applications that can fall into the PUA category might be considered useful by some users.
More annoying than malicious
Ransomware
Ransomware typically encrypts the victim's files, making them inaccessible, and demands a ransom payment to decrypt them. recovering the files without the decryption key is an intractable problem – and difficult to trace digital currencies such as Ukash and cryptocurrency are used for the ransoms.
Very damaging
Rootkits
Not in itself malware but can loaded onto your machine to spread forms of malware. A rootkit can be a computer virus which consists of a program (or combination of several programs) designed to take fundamental control (in UNIX terms "root" access, in Windows "Administrator" access) of a computer system, without authorization by the system's owners and legitimate managers.
Typically, rootkits act to obscure their presence on the system through subversion or evasion of standard operating system security mechanisms. Can contain viruses or other forms of malware. The only way to securely remove theses is to erase the hard drive of your computer.
Can contain viruses or other forms of malware. The only way to securely remove theses is to erase the hard drive of your computer.
Scareware
Scareware comprises several classes of scam software, often with limited or no benefit, sold to consumers via certain unethical marketing practices.
Spyware
Spyware is computer software that is installed surreptitiously on a personal computer to intercept or take partial control over the user's interaction with the computer, without the user's informed consent.
Trojans
In the context of computing and software, a Trojan horse, also known as a Trojan, is malware that appears to perform a desirable function but in fact performs undisclosed malicious functions. Therefore, a computer worm or virus may be a Trojan horse. The term is derived from the classical story of the Trojan horse.
Virus
A computer virus is a computer program that can copy itself and infect a computer without permission or knowledge of the user.
It can delete all your information from letters to photos. It can easily spread to other computers.
Worms
A computer worm is a self-replicating computer program. It uses a network to send copies of itself to other nodes (computer terminals on the network) and it may do so without any user intervention. Unlike a virus, it does not need to attach itself to an existing program. Worms almost always cause harm to the network, if only by consuming bandwidth, whereas viruses almost always corrupt or modify files on a targeted computer.
This can drastically slow your computer. Some worms act like viruses and can damage the information on your machine