Malware is a portmanteau of "malicious" and "software". As the name implies, malware is created solely to harm and inconvenience people by corrupting devices and/or data.
Malware runs the gamut of "black hat" software developers wanting a laugh for the wrong reasons to criminal organizations and the intelligence community who want to access their targets' devices and networks to get their data.
Types of Malware
There are several kinds of malware that damage their targets in different ways. This list isn't exhaustive, but these are the most common types of malware:
Similar to viral diseases humans get, computer viruses latch onto clean files then start spreading to other files. Viruses aim to corrupt or delete files and spread to the point of ruining the system's core function.
Adware isn't always as malicious as viruses, worms, and other types of malware, but it's definitely bothersome and can also present security risks. It exists mostly to annoy users and get them to accidentally click on pop-ups or tabs that contain other malware.
Spyware is meant to do just that: spy on you. Your online activity and things like passwords, credit card numbers, and other sensitive information is spied on for another user to do anything from commit identity theft to using your data against you in more subtle ways.
Similar to viruses, worms infect via networks by using the devices' interfaces. Worms can function through local networks or an internet connection. Also similarly to viruses corrupting files and spreading, worms use each consecutive networked device to spread their infection. In the same family as worms, botnets are networks of corrupted computers or devices that work in tandem.
Named after the famous Trojan horse full of soldiers on the offense, Trojans embody the exact same concept by looking similar to real software or being included in real software packages that were tampered with. Trojans aren't as blunt or fast-acting as viruses in that they tend to find or create holes in your security to let other types of malware in easily.
Ransomware is more common with small business and enterprise networks as well as high-profile individuals. Also known as scareware, ransomware locks down devices and threatens to leak or erase all the data within unless the victim pays the attacker a ransom.
All of these types of software fit under the malware umbrella since their primary purpose is to harm the users by compromising identity information, corrupting their data, or deleting it.