Adversaries may use [Obfuscated Files or Information](https://attack.mitre.org/techniques/T1027) to hide artifacts of an intrusion from analysis. They may require separate mechanisms to decode or deobfuscate that information depending on how they intend to use it. Methods for doing that include built-in functionality of malware or by using utilities present on the system.

One such example is the use of [certutil](https://attack.mitre.org/software/S0160) to decode a remote access tool portable executable file that has been hidden inside a certificate file.(Citation: Malwarebytes Targeted Attack against Saudi Arabia) Another example is using the Windows <code>copy /b</code> command to reassemble binary fragments into a malicious payload.(Citation: Carbon Black Obfuscation Sept 2016)

Sometimes a user's action may be required to open it for deobfuscation or decryption as part of [User Execution](https://attack.mitre.org/techniques/T1204). The user may also be required to input a password to open a password protected compressed/encrypted file that was provided by the adversary. (Citation: Volexity PowerDuke November 2016)
Deobfuscate/Decode Files or Information
source_name: mitre-attack  url: https://attack.mitre.org/techniques/T1140  external_id: T1140     source_name: Volexity PowerDuke November 2016  description: Adair, S.. (2016, November 9). PowerDuke: Widespread Post-Election Spear Phishing Campaigns Targeting Think Tanks and NGOs. Retrieved January 11, 2017.  url: https://www.volexity.com/blog/2016/11/09/powerduke-post-election-spear-phishing-campaigns-targeting-think-tanks-and-ngos/     source_name: Malwarebytes Targeted Attack against Saudi Arabia  description: Malwarebytes Labs. (2017, March 27). New targeted attack against Saudi Arabia Government. Retrieved July 3, 2017.  url: https://blog.malwarebytes.com/cybercrime/social-engineering-cybercrime/2017/03/new-targeted-attack-saudi-arabia-government/     source_name: Carbon Black Obfuscation Sept 2016  description: Tedesco, B. (2016, September 23). Security Alert Summary. Retrieved February 12, 2018.  url: https://www.carbonblack.com/2016/09/23/security-advisory-variants-well-known-adware-families-discovered-include-sophisticated-obfuscation-techniques-previously-associated-nation-state-attacks/     