Defense Evasion: Base64 Encoded Shell Script Executed

This document describes a threat finding type in Security Command Center. Threat findings are generated by threat detectors when they detect a potential threat in your cloud resources. For a full list of available threat findings, see Threat findings index.

Overview

A process was executed that contains an argument that that is a base64 encoded shell script. If an encoded shell script execution is detected, it is a signal that an attacker is trying encode binary data for transfer to ASCII-only command lines. Attackers can use this technique to evade detection and run malicious code embedded in a shell script.

Cloud Run Threat Detection is the source of this finding.

How to respond

To respond to this finding, do the following:

Review finding details

  1. Open the Defense Evasion: Base64 Encoded Shell Script Executed finding as directed in Reviewing findings. Review the details on the Summary and JSON tabs.

  2. On the Summary tab, review the information in the following sections.

    • What was detected, especially the following fields:
      • Program binary: the absolute path of the executed binary
      • Arguments: the arguments passed during binary execution
    • Affected resource, especially the following fields:

  3. On the JSON tab, note the following fields.

    • resource:
      • project_display_name: the name of the project that contains the affected Cloud Run resource
    • finding:
      • processes:
        • binary:
        • path: the full path of the executed binary
      • args: the arguments that were provided when the binary was executed

  4. Identify other findings that occurred at a similar time for the affected container. Related findings might indicate that this activity was malicious, instead of a failure to follow best practices.

  5. Review the settings of the affected container.

  6. Check the logs for the affected container.

Research attack and response methods

  1. Review MITRE ATT&CK framework entries for this finding type: Defense Evasion: Obfuscated Files or Information.
  2. To develop a response plan, combine your investigation results with MITRE research.

Implement your response

For response recommendations, see Respond to Cloud Run threat findings.

What's next