This rule detects the presence of the Cryptic20 Tughack malware, a known threat actor tool often used for initial access or lateral movement within enterprise networks. Proactively hunting for this signature allows the SOC team to identify dormant or low-noise infections that may have evaded standard behavioral detections, ensuring timely remediation in the Azure Sentinel environment.
rule Cryptic20Tughack
{
meta:
author="malware-lu"
strings:
$a0 = { B8 00 00 40 00 BB [3] 00 B9 00 10 00 00 BA [3] 00 03 D8 03 C8 03 D1 3B CA 74 06 80 31 ?? 41 EB F6 FF E3 }
condition:
$a0 at pe.entry_point
}This YARA rule can be deployed in the following contexts:
This rule contains 1 string patterns in its detection logic.
Scenario: A DevOps engineer runs a custom Python-based automation script (e.g., deploy_helper.py) that uses the crypt module or embeds a small, obfuscated payload for internal service-to-service authentication. The script’s binary structure or string patterns match the “Cryptic” heuristic in the YARA rule, triggering a false positive during a routine CI/CD pipeline execution.
jenkins.exe, gitlab-runner.exe, or azure-pipelines-agent.exe) if the parent process is a known build tool and the file path resides in the standard workspace directory (e.g., C:\jenkins\workspace\).Scenario: An IT administrator uses a legitimate, open-source utility like 7-Zip or WinRAR to compress a large log archive for off-site backup. The compression algorithm or the resulting archive’s header structure inadvertently matches the “Tughack” string pattern or entropy threshold defined in the YARA rule, especially if the archive contains mixed file types with high entropy.
.7z, .rar, and .zip if the process is 7z.exe, WinRAR.exe, or WinRAR.exe and the file size is greater than 10MB (indicating a bulk archive rather than a small executable).Scenario: A security team runs a memory scanning tool like Volatility3 or Rekall on a live host to investigate a suspected incident. The tool’s own binary or the memory dump files it generates contain embedded strings or code patterns that resemble the “Cryptic20” signature, causing the YARA rule to flag the scanner itself as malicious.