Opcode obfuscation is an anti-disassembling technique that involves modifying the opcodes of a program's machine language instructions in order to make it more difficult for a disassembler to accurately reconstruct the original instructions. This can be done in a variety of ways, such as by using equivalent but different opcodes for the same operation, by adding additional instructions or data to the program, or by rearranging the program's instructions in a non-standard order.

Opcode obfuscation is a common technique used by malware authors and other attackers to make it more difficult for analysts to disassemble and understand their programs. It can be used in conjunction with other anti-disassembling techniques, such as the call trick or the insertion of garbage bytes, to create even more effective and powerful exploits.