UPX – Ultimate tiny packer for any eXecutable file

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UPX (short for Ultimate Packer for eXecutables) is a classic, illustrious universal and extendable lightweight packer for various executable files (such as EXE, DLL). With excellent compression ratio and very fast decompression speed. And can be regarded as a commercial quality freeware!

UPX supports executable file formats on almost any platform, such as DOS, Windows, Mac OS X, Linux, BSD, etc. It has very good compression ratio (compressed executables dwindle 50%~70% in size). And more important, the executable or library file compressed by UPX does not loss any function, they can run normally just like before. In fact, UPX has not adverse effects on running time or memory usage for most of the supported file formats.

In addition to being used to compress the executable file to save a lot of storage space, UPX has another infamous and main purpose – packing (add a shell) trojans and viruses (a common way of protecting executable files). The packed executable program can be run directly, but does not allow to view its source code (unless unpack the shell first) – so as to avoid killing by antivirus software easily.

// Prompts //

  • This is a DOS program, that means you can and have to operate it in the command line.

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