Chinese Hacktool Set - file hydra.exe

Hunt Hypothesis

This detection identifies the presence of hydra.exe, a known component of the Chinese Hacktool set often associated with credential harvesting and lateral movement activities within targeted environments. SOC teams should proactively hunt for this artifact in Azure Sentinel to validate its legitimacy against baseline inventory, as its low severity rating may mask sophisticated, persistent adversary operations that require deeper contextual analysis before remediation.

YARA Rule

rule hydra_7_3_hydra {
	meta:
		description = "Chinese Hacktool Set - file hydra.exe"
		author = "Florian Roth"
		reference = "http://tools.zjqhr.com/"
		date = "2015-06-13"
		hash = "2f82b8bf1159e43427880d70bcd116dc9e8026ad"
	strings:
		$s1 = "[ATTEMPT-ERROR] target %s - login \"%s\" - pass \"%s\" - child %d - %lu of %lu" fullword ascii
		$s2 = "(DESCRIPTION=(CONNECT_DATA=(CID=(PROGRAM=))(COMMAND=reload)(PASSWORD=%s)(SERVICE" ascii
		$s3 = "cn=^USER^,cn=users,dc=foo,dc=bar,dc=com for domain foo.bar.com" fullword ascii
		$s4 = "[%d][smb] Host: %s Account: %s Error: ACCOUNT_CHANGE_PASSWORD" fullword ascii
		$s5 = "hydra -P pass.txt target cisco-enable  (direct console access)" fullword ascii
	condition:
		uint16(0) == 0x5a4d and filesize < 700KB and 1 of them
}

Deployment Notes

This YARA rule can be deployed in the following contexts:

• Microsoft Defender for Endpoint — Custom indicators / advanced hunting
• Email Gateway — Attachment scanning
• File Share Monitoring — Periodic scanning of shared drives
• YARA CLI — Manual threat hunting on endpoints

This rule contains 5 string patterns in its detection logic.

References

• http://tools.zjqhr.com/
• Source Rule

False Positive Guidance

Here are 5 specific false positive scenarios for the Chinese Hacktool Set - file hydra.exe detection rule, along with suggested filters or exclusions:

• Password Auditing via John the Ripper Wrapper

  • Scenario: The IT Security team utilizes a custom wrapper script to run hydra.exe (a common name for password auditing tools like Hashcat wrappers or specific Chinese security suites) during monthly credential audits. This process scans Active Directory hashes stored on a dedicated file server.
  • Filter/Exclusion: Create an exclusion rule that ignores alerts where the parent process is the scheduled task runner (svchost.exe running under System) and the execution path matches the known audit directory (e.g., C:\Program Files\SecurityAudit\bin\hydra.exe).

• Automated Network Connectivity Testing

  • Scenario: The DevOps team has a scheduled job that runs every morning at 02:00 to test network latency and service availability across regional branches. They use a legacy Chinese networking utility named hydra.exe deployed on the primary jump host (JUMP-HOST-01).
  • Filter/Exclusion: Exclude events where the source IP is the static address of the Jump Host (e.g., 192.168.10.5) and the process command line contains specific flags used for connectivity checks, such as -mode scan or -target internal.

• Endpoint Protection Agent Updates

  • Scenario: The organization uses a third-party Endpoint Detection and Response (EDR) solution from a Chinese vendor (e.g., Qihoo 360 or Kingsoft). During the daily update cycle, the agent extracts a temporary utility named hydra.exe to verify file integrity before installing patches.
  • Filter/Exclusion: Filter out alerts where