Encrypted or Encoded File Payload Detection Strategy

ID: DET0087
Domains: Enterprise
Analytics: AN0237, AN0238, AN0239
Version: 1.0
Created: 21 October 2025
Last Modified: 21 October 2025

Analytics

AN0237

Detection of processes that load or decode encrypted/encoded files in memory and subsequently execute or inject them, indicating payload unpacking or memory-resident malware.

Log Sources
Data Component Name Channel
Module Load (DC0016) WinEventLog:Sysmon EventCode=7
Process Access (DC0035) WinEventLog:Sysmon EventCode=10
Process Creation (DC0032) WinEventLog:Security EventCode=4688
Mutable Elements
Field Description
Image Path of decoder utilities (e.g., certutil.exe, powershell.exe) can vary across environments.
CommandLine Base64/hex strings used may change per encoded payload.
TimeWindow The duration between file decode and execution may differ across implementations.

AN0238

Detection of suspicious use of shell utilities or scripts that decode or decrypt a payload and execute it without writing to disk.

Log Sources
Data Component Name Channel
Process Creation (DC0032) auditd:SYSCALL execve
Network Connection Creation (DC0082) linux:Sysmon EventCode=22
Mutable Elements
Field Description
UserContext Normal usage of `base64`, `openssl`, or `gpg` varies by user/role.
ProcessLineage Parent-child process chains may differ across deployments.
TimeWindow Time between decode and execution is implementation-specific.

AN0239

Detection of encoded payloads being decoded and executed in-memory using scripting tools or third-party decoders.

Log Sources
Data Component Name Channel
Command Execution (DC0064) macos:unifiedlog log stream
Process Creation (DC0032) macos:endpointsecurity es_event_exec
Process Modification (DC0020) macos:unifiedlog memory mapping
Mutable Elements
Field Description
ScriptContent Encoded payload content varies across adversaries.
ExecutionChain Sequence of tools or scripts executed can differ.
UserContext May depend on whether user is admin, daemon, or system account.