Malware is short for malicious software, and is used as a general term to describe basically anything that harms your computer or steals your information. Malware may spread through portable media such as flash disks, floppies and CDs, or access the computer system via insecure networks or online downloads. Malware includes computer viruses, worms, trojan horses, spyware, dishonest adware, scareware, crimeware, most rootkits, and any other malicious and unwanted software or program.
People often refer to malware as a computer virus, but they are not the same thing. Viruses have the ability to reproduce and make copies of themselves. They can also spread from one computer to another. Most viruses attach themselves to executable files, but some infect Microsoft Office Macros, autorun scripts, or if the virus is really destructive, the master boot record.
Computer Worms exploit a security hole in a computer to quickly infect other computers in the network, often without anyone knowing. They are often transferred from one computer to another by email, when an unsuspecting person opens an email attachment.
Trojan Horses are applications that look like they do something good, but instead have malicious code that does, well of course, malicious things. Unlike computer viruses, trojans can not replicate themselves, so they have to be installed by an unsuspecting user. Many trojans often create a backdoor, which the hacker can exploit to gain control of your computer system.
Spyware does exactly what its name tells you- it spies on your system. It collects information without you knowing, and sends that back to the creator to be used in malicious ways. Spyware is often used to collect information about your online accounts, such as your bank account. Then it sends this information back to the creator, who can gain control of your bank account and steal your money.
While this can be classified as a trojan horse, scareware is any application that tricks you into downloading their software, such as a fake antivirus. Then the software supposedly scans your computer and finds a bunch of malware. However to remove the malware, you need to purchase a license to the full program. Scareware often holds your computer “hostage”- you can’t uninstall the fake antivirus or sometimes even use the computer- until you purchase the fake antivirus or pay the ransom.
Adware is any software package that automatically plays, displays, or downloads advertisements to a computer. Adware is the least intrusive compared to the other types of malware, but some adware may come with integrated spyware such as keyloggers. Thge purpose of adware is to generate revenue for its author.
A rootkit is any software that allows “root” or administrator access to the system. Rootkits are often bundled with other forms of malware. Rootkits are often hard to find and remove due to the fact that a rootkit can bypass the software that is supposed to find it. Rootkits target firmware, a hypervisor, the kernel, or, most commonly, user-mode applications.