false positives may be present and will require some tuning based on processes. filter as needed.

Techniques

T1027

Sample rules

Linux Obfuscated Files or Information Base64 Decode

source: splunk
technicques:
- T1027

Description

The following analytic detects the use of the base64 decode command on Linux systems, which is often used to deobfuscate files. It leverages data from Endpoint Detection and Response (EDR) agents, focusing on command-line executions that include “base64 -d” or “base64 –decode”. This activity is significant as it may indicate an attempt to hide malicious payloads or scripts. If confirmed malicious, an attacker could use this technique to execute hidden code, potentially leading to unauthorized access, data exfiltration, or further system compromise.

Detection logic


| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime FROM datamodel=Endpoint.Processes
  WHERE Processes.process_path="*/base64" Processes.process="*-d*"
  BY Processes.action Processes.dest Processes.original_file_name
     Processes.parent_process Processes.parent_process_exec Processes.parent_process_guid
     Processes.parent_process_id Processes.parent_process_name Processes.parent_process_path
     Processes.process Processes.process_exec Processes.process_guid
     Processes.process_hash Processes.process_id Processes.process_integrity_level
     Processes.process_name Processes.process_path Processes.user
     Processes.user_id Processes.vendor_product

| `drop_dm_object_name(Processes)`

| `security_content_ctime(firstTime)`

| `security_content_ctime(lastTime)`

| `linux_obfuscated_files_or_information_base64_decode_filter`