Executable compression is any means of compressing an executable file and combining the compressed data with the decompression code it needs into a single executable. Its principal actual purpose is to deter Reverse engineering, to hide malware (from Antivirus scans) by proprietary methods and/or added encryption.

When executed, this will unpack the original executable code and transfer control to it. The effect is the same as if the original uncompressed executable had been run. A compressed executable requires

• less storage space in the file system,
• less time to transfer data from the file system into memory, and
• more time to decompress the data before execution begins than the uncompressed original.

A compressed executable is one variety of executable archive, where the compressed data happens to be itself an executable file.

There are tools that will decompress a compressed executable without executing it, such as CUP386 and UNP.

Most packed executables decompress directly into the memory and need no free file system space to start. However, some decompressor stubs are known to write the uncompressed executable in the file system in order to start it.

Executable compression has often been taken to extremes by the demoscene, and some compressors, such as MuCruncher, kkrunchy and 624, have been specifically designed for use in size-restricted demos. An extreme example is Crinkler, which has been created for 4096 byte intros, and is physically unable to compress much larger executables because of the compression time and memory consumption.

List of packers

For Portable Executable files on Microsoft Windows

1. .netshrink
2. ASPack
3. CExe
4. exe32pack
5. eXPressor
6. FSG
7. MEW - development stopped
8. MuCruncher
9. NeoLite
10. NsPack - .NET
11. PECompact
12. PEPack
13. PELock
14. PKLite32
15. PEtite
16. Shrinker32
17. Upack - Freeware
18. UPX - Open source
19. WWPack
20. PESpin

For DOS-based executables

1. apack
2. LZEXE
3. diet
4. PKLite
5. 32LiTE
6. 624 (small .COMs < 25KiB only)
7. UPX

For other executable formats

1. 624 - for ELF binaries on Linux/i386
2. gzexe - uses a shell script stub and gzip and works on most Unix-like systems
3. PuCrunch - for Commodore 64, 16 and VIC 20.
4. Exomizer - for Commodore 64, 16 and VIC 20, etc...
5. ByteBoozer PC - for Commodore 64.
6. powerpacker - for Commodore Amiga
7. Titanics cruncher - for Commodore Amiga
8. imploder - for Commodore Amiga
9. TNM cruncher - for Commodore Amiga
10. UPX - also supports Linux/i386 binaries, as well as some more obscure platforms

List of unpackers and identifiers

• PEiD
• CUP386 (generic unpacker/debugger, freeware)
• UNP (specific/generic unpacker, cardware)
• IUP (generic unpacker, public domain w/ .ASM src)

See also

• Data compression
• Executable
• Kolmogorov complexity

EXE packers

Kompression ausführbarer Programmdateien | Упаковка исполняемых файлов