Find sigma rule 
Attack: Deobfuscate/Decode Files or Information
Adversaries may use Obfuscated Files or Information 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 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 copy /b 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. 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)
MITRE
Tactic
- defense-evasion
technique
- T1140
Test : Certutil Rename and Decode
OS
- windows
Description:
Rename certutil and decode a file. This is in reference to latest research by FireEye here
Executor
command_prompt
Sigma Rule
-
proc_creation_win_calc_uncommon_exec.yml (id: 737e618a-a410-49b5-bec3-9e55ff7fbc15)
-
proc_creation_win_susp_copy_system_dir.yml (id: fff9d2b7-e11c-4a69-93d3-40ef66189767)
-
proc_creation_win_renamed_binary.yml (id: 36480ae1-a1cb-4eaa-a0d6-29801d7e9142)
-
proc_creation_win_susp_non_exe_image.yml (id: c09dad97-1c78-4f71-b127-7edb2b8e491a)
-
proc_creation_win_renamed_binary_highly_relevant.yml (id: 0ba1da6d-b6ce-4366-828c-18826c9de23e)