An exe file (pronounced as letters E-X-E) is a computer file that ends with the extension ".exe" otherwise known as an executable file. When one clicks on an exe file, a built-in routine automatically executes code that can set several functions into motion. Exe files are used to install and run programs and routines.

An exe file is just one of several file format types that are recognized by various operating systems. Text files, which are files that do not generate code but simply display text, end in txt. Microsoft Word saves files with the doc extension, short for document. Another common file type is the compressed or zipped file, which uses the zip extension.

The exe file is one of the most useful types of files precisely because it runs programs; however, this also makes it potentially harmful. It can be used as a delivery system for viruses or other malicious routines. Outwardly, the infected exe file might seem quite benign. Clicking on it might appear to launch nothing more than an animated cartoon or simple arcade game. However, unseen code can be running in the background, infecting or compromising the computer.

If one clicks on a malicious exe file, over the next several hours or days the computer might become unstable. Often the user does not relate the problem back to the cause and attributes it to other factors, such as the need to defragment or replace a disk. Personal information or password keystrokes might be handed over to an unknown website without knowledge of the user, or the machine might delete its own files and crash altogether. Any of these scenarios and more can be set in motion by simply clicking on a 'bad' exe file.

Because of the potential harm, when downloading any exe file it's a good idea to scan it with a reputable virus scanner before clicking on it. To this end, security experts recommend setting browsers so that websites cannot load programs automatically. This gives the surfer the chance to monitor which programs get passed to his or her computer.

Exe files are generally not meant to be edited, and changing an exe's file size will render it inoperable. Since the exe file is most often a program, it is routinely protected by copyright laws, per the linked license agreement issued by its author. Hacking an exe file is illegal in this case. The exception is public domain software. Public domain software belongs to the public and can legally be altered by anyone.

As it is safest to err on the side of caution, the best defense is a good offense. Experts recommend keeping virus checkers up to date and deleting email from unknown sources. If you receive an exe file from someone you trust, scan it first before clicking on it. Even files that appear to be coming from reputable sources can be maligned by third parties without the source's knowledge.