[Guide] Extensions which you don't want to open!

Dangerous and malicious file extension list

Group of file extensions, which can be dangerous and harmful for your computer, but it may be also a regular program or data files. You should run a virus scan before opening any unknown file type from this group.
Malicious software, also known as malware, is an application or a file, which is harmful to the computer user. Malicious software includes computer viruses, worms, trojan horses, spyware, adware or rootkits.
Computer virus - virus is a program or programming code, which replicates by being copied or initiating its copying to another program, computer boot sector or document. Viruses can be transmitted as attachments to an e-mail note or in a downloaded file, or can be present on a diskette or CD. Some viruses wreak their effect as soon as their code is executed, other lie dormant until circumstances cause their code to be executed by the computer.
Computer worm - worm is a self-replicating virus, which does not alter files, but resides in active memory and duplicates itself. Worms use parts of the operating system that are automatic and usually invisible to the user. It is common for worms to be noticed only after their uncontrolled replication consumes system resources, slowing or halting other tasks.
Trojan horses - trojan horse (also known as trojan), is non-self-replicating malware, which appears to perform a desirable function for the user, while facilitates unauthorized access to the user's computer system.
Spyware - spyware is any technology, which aids in gathering information about a person or organization without their knowledge. Spyware is a program that is installed in someone's computer to secretly gather information about the user and to relay it to advertisers or other interested parties. Spyware can get in the computer as a software virus or as the result of installing a new program.
Adware - adware is any software package, which automatically plays, displays or downloads advertisements to the computer after the software is installed on it or while the application is being used.
Rootkits - rootkit is a collection of programs that enable administrator-level access to a computer or computer network. Typically, a cracker installs a rootkit on a computer after first obtaining user-level access, either by exploiting a known vulnerability or cracking the password. Once the rootkit is installed, it allows the attacker to mask intrusion and gain root or privileged access to the computer and possibly also to other machines in the network.