Adversaries may use junk code / dead code to obfuscate a malware’s functionality. Junk code is code that either does not execute, or if it does execute, does not change the functionality of the code. Junk code makes analysis more difficult and time-consuming, as the analyst steps through non-functional code instead of analyzing the main code. It also may hinder detections that rely on static code analysis due to the use of benign functionality, especially when combined with Compression or Software Packing.[1],[2]
No-Operation (NOP) instructions are an example of dead code commonly used in x86 assembly language. They are commonly used as the 0x90 opcode. When NOPs are added to malware, the disassembler may show the NOP instructions, leading to the analyst needing to step through them.[1]
The use of junk / dead code insertion is distinct from Binary Padding because the purpose is to obfuscate the functionality of the code, rather than simply to change the malware’s signature.
References
- ReasonLabs. (n.d.). What is Dead code insertion?. Retrieved March 4, 2025.
- What is Junk Code?. (n.d.). ReasonLabs. Retrieved April 4, 2025.
Ticket collegati
| Tipo di collegamento | Ticket |
|---|---|
| is related to | Techniques |
| is blocked by | Detection Strategy for Junk Code Obfuscation with Suspicious Execution Patterns |
| is blocked by | Antivirus/Antimalware |
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