List of Common Malware Types:

Malware, short for malicious software, is any software used to disrupt computer operations, gather sensitive information, gain access to private computer systems, or display unwanted advertising.^[1] Malicious software was called computer virus before the term malware was coined in 1990 by Yisrael Radai.^[2] The first category of malware propagation concerns parasitic software fragments that attach themselves to some existing executable content. The fragment may be machine code that infects some existing application, utility, or system program, or even the code used to boot a computer system.^[3] Malware is defined by its malicious intent, acting against the requirements of the computer user, and does not include software that causes unintentional harm due to some deficiency.
Malware may be stealthy, intended to steal information or spy on computer users for an extended period without their knowledge, as for example Reign, or it may be designed to cause harm, often as sabotage (e.g., Stuxnet), or to extort payment (Crypto Locker). 'Malware' is an umbrella term used to refer to a variety of forms of hostile or intrusive software,^[4] including computer viruses, worms, trojan horses, ransomware, spyware, adware, scare ware, and other malicious programs. It can take the form of executable code, scripts, active content, and other software.^[5] Malware is often disguised as, or embedded in, non-malicious files. As of 2011 the majority of active malware threats were worms or trojans rather than viruses.^[6]
In law, malware is sometimes known as a computer contaminant, as in the legal codes of several U.S. states.
Spyware or other malware is sometimes found embedded in programs supplied officially by companies, e.g., downloadable from websites, that appear useful or attractive, but may have, for example, additional hidden tracking functionality that gathers marketing statistics. An example of such software, which was described as illegitimate, is the Sony root kit, a Trojan embedded into CDs sold by Sony, which silently installed and concealed itself on purchasers' computers with the intention of preventing illicit copying; it also reported on users' listening habits, and unintentionally created vulnerabilities that were exploited by unrelated malware.^[9]
Software such as anti-virus, anti-malware, and firewalls are used to protect against activity identified as malicious, and to recover from attacks.^[10]

This list of Malware types only scratches the surface in that Malware is being developed by those trying to gain access to your computer for monetary gain. The list of Malware types focuses on the most common and the general categories of infection

1. Adware:. The least dangerous and most lucrative Malware. Adware displays ads on your computer.
2. Spyware:. Spyware is software that spies on you, tracking your internet activities in order to send advertising (Adware) back to your system.
3. Virus: A virus is a contagious program or code that attaches itself to another piece of software, and then reproduces itself when that software is run. Most often this is spread by sharing software or files between computers.
4. Worm: A program that replicates itself and destroys data and files on the computer. Worms work to “eat” the system operating files and data files until the drive is empty.
5. Trojan: The most dangerous Malware. Trojans are written with the purpose of discovering your financial information, taking over your computer’s system resources, and in larger systems creating a “denial-of-service attack” Denial-of-service attack: an attempt to make a machine or network resource unavailable to those attempting to reach it. Example: AOL, Yahoo or your business network becoming unavailable.
6. Root kit: This one is likened to the burglar hiding in the attic, waiting to take from you while you are not home. It is the hardest of all Malware to detect and therefore to remove; many experts recommend completely wiping your hard drive and reinstalling everything from scratch. It is designed to permit the other information gathering Malware in to get the identity information from your computer without you realizing anything is going on.
7. Backdoors: Backdoors are much the same as Trojans or worms, except that they open a “backdoor” onto a computer, providing a network connection for hackers or other Malware to enter or for viruses or SPAM to be sent.
8. Key loggers: Records everything you type on your PC in order to glean your log-in names, passwords, and other sensitive information, and send it on to the source of the key logging program. Many times key loggers are used by corporations and parents to acquire computer usage information.  
9. Rogue security software: This one deceives or misleads users. It pretends to be a good program to remove Malware infections, but all the while it is the Malware. Often it will turn off the real Anti-Virus software. The next image shows the typical screen for this Malware program, Antivirus 2010
10. Ransomware: If you see this screen that warns you that you have been locked out of your computer until you pay for your cyber-crimes. Your system is severely infected with a form of Malware called Ransomware. It is not a real notification from the FBI, but, rather an infection of the system itself. Even if you pay to unlock the system, the system is unlocked, but you are not free of it locking you out again. The request for money, usually in the hundreds of dollars is completely fake.
11. Browser Hijacker:  When your homepage changes to one that looks like those in the images inserted next, you may have been infected with one form or another of a Browser Hijacker. This dangerous Malware will redirect your normal search activity and give you the results the developers want you to see. Its intention is to make money off your web surfing. Using this homepage and not removing the Malware lets the source developers capture your surfing interests. This is especially dangerous when banking or shopping online. These homepages can look harmless, but in every case they allow other more infectious