Shellcode Runner in C with RC4 Encryption

Example illustrating how to use basic encryption to obfuscate a payload in order to evade AV. Two C programs: One encrypts shellcode via RC4; The other decrypts the RC4-encrypted shellcode at runtime and executes it.

How to use

1. Add your unencrypted shellcode to source file encrypt_shellcode.c and modify rc4 password if desired. If you change password, make sure you update it in encrypt_shellcode.c and execute_encrypted_shellcode.c
2. Build gcc -s encrypt_shellcode.c -o encrypt_shellcode.exe and run encrypt_shellcode.exe
3. Copy output from encrypt_shellcode.exe and into source file execute_encrypted_shellcode.c
4. Build gcc -s execute_encrypted_shellcode.c -o execute_encrypted_shellcode.exe
5. Running execute_encrypted_shellcode.exe will decrypt and then execute the shellcode

References

1. Red Teaming 101: Executing Malicious Shellcode with C — a guide for beginners
2. A Beginner's Guide to Windows Shellcode Execution Techniques