metame is a simple metamorphic code engine for arbitrary executables. From Wikipedia: Metamorphic code is code that when run outputs a logically equivalent version of its own code under some interpretation. This is used by computer viruses to avoid the pattern recognition of anti-virus software. metame implementation works this way: Open a given binary and analyze the code Randomly replace instructions with equivalences in logic and size Copy and patch the original binary to generate a mutated variant It currently supports the following architectures: x86 32 bits x86 64 bits Also, it supports a variety of file formats, as radare2 is used for file parsing and code analysis. Example of code before and after mutation: Hint: Two instructions have been replaced in this snippet. Here another example on how it can mutate a NOP sled into equivalent code: Installation pip install metame This should also install the requirements. You will also need radare2 . Refer to the official website for installation instructions. simplejson is also a “nice to have” for a small performance boost: pip install simplejson Usage metame -i original.exe -o mutation.exe -d Use metame -h for help. Download Metame