ESXi Shell Command Obfuscation

Last updated 2 days ago on 2026-09-30

Created 2 days ago on 2026-09-30

About

Detects ESXi shell commands that rebuild a command with encoding instead of writing it in clear text, including octal and hex `printf`, Python `chr()`, `awk` `%c` sequences, reversed strings, and invisible Unicode. The shell log then hides the administrative command. The decoded action can still change syslog, the firewall, or other host settings.

Tags

Domain: EndpointData Source: VMware vSphereUse Case: Threat DetectionTactic: Defense EvasionTactic: ExecutionRule Type: Custom Query (KQL)Platform: VMware ESXiThreat: Encoding-Based ObfuscationLanguage: kuery

Severity

high

Risk Score

MITRE ATT&CK™

Defense Evasion (TA0005)(external, opens in a new tab or window)

↳ Obfuscated Files or Information (T1027)(external, opens in a new tab or window)

Execution (TA0002)(external, opens in a new tab or window)

↳ Command and Scripting Interpreter (T1059)(external, opens in a new tab or window)

False Positive Examples

Rare troubleshooting one-liners can use `printf` or `awk` to generate text. A line that also decodes to a syslog, firewall, or VM command should still be investigated.

License

Elastic License v2(external, opens in a new tab or window)

Definition

Rule Type: Query (Kibana Query Language)
Integration Pack: Prebuilt Security Detection Rules
Index Patterns: logs-vsphere.log-*
Related Integrations: vsphere(external, opens in a new tab or window)
Query

✄𐘗text code block:
✄𐘗data_stream.dataset: "vsphere.log" and (
  message: (
    "chr(101)" or
    "%c%c%c%c%c%c" or
    "ilcxse" or
    "0xe2,0x80,0x8b" or
    "0xf3,0xb0,0x80,0x80" or
    "\\x65\\x73\\x78" or
    "\\145\\163\\170"
  )
)

Install detection rules in Elastic Security

Detect ESXi Shell Command Obfuscation in the Elastic Security detection engine by installing this rule into your Elastic Stack.

To setup this rule, check out the installation guide for Prebuilt Security Detection Rules(external, opens in a new tab or window).