Linux Decode Base64 to Shell
The following analytic detects the behavior of decoding base64-encoded data and passing it to a Linux shell. Additionally, it mitigates the potential damage and protects the organization's systems and data.The…
Description
The following analytic detects the behavior of decoding base64-encoded data and passing it to a Linux shell. Additionally, it mitigates the potential damage and protects the organization's systems and data.The detection is made by searching for specific commands in the Splunk query, namely "base64 -d" and "base64 --decode", within the Endpoint.Processes data model. The analytic also includes a filter for Linux shells. The detection is important because it indicates the presence of malicious activity since Base64 encoding is commonly used to obfuscate malicious commands or payloads, and decoding it can be a step in running those commands. It suggests that an attacker is attempting to run malicious commands on a Linux system to gain unauthorized access, for data exfiltration, or perform other malicious actions.
Detection logic
Detection requirements
- Platform
- ESXiLinuxmacOSNetwork DevicesWindows
The rule states no platform. This is derived from the 2 ATT&CK techniques it maps to.
- Log source category
- cisco_isovalent_process_execsysmon_for_linux_eventid_1
Known benign triggers
- False positives may be present based on legitimate software being utilized. Filter as needed.
MITRE ATT&CK mappings
0 exclusive techniques.This is coverage no other published rule has; it is not this rule's total technique count.
References
| Reference | Cited by |
|---|---|
| github.com/redcanaryco/atomic-red-team/blob/388942adbd9641f4dfdcf079d7efe9a75ec0ac43/atomics/T1140/T1140.yaml#L240 | 3 |
| github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1027/T1027.md#atomic-test-1---decode-base64-data-into-script | 2 |
| linux.die.net/man/1/base64 | 2 |
| redcanary.com/blog/lateral-movement-with-secure-shell/ | 4 |
From the source
- At source
- Open at source
- Upstream identifier
- 637b603e-1799-40fd-bf87-47ecbd551b66
- Tagged by the source as
- Cisco Isovalent Suspicious ActivityLinux Living Off The LandEndpointendpointSplunk CloudSplunk EnterpriseSplunk Enterprise Securityendpoint
Licence
- Published under
- Apache License 2.0Read the licence
- Attribution
- Required
- Obtained under
- Apache-2.0Read the origin licence
Authorship
- Written by
- Published
- Oct 13, 2026
- Version
- 2