ABCCryptor10byZloY

Hunt Hypothesis

This rule identifies the presence of the ABCCryptor ransomware variant, a tool known for encrypting files and leaving specific artifacts that indicate active compromise or staging. Proactively hunting for this signature allows the SOC to detect early-stage ransomware deployment or dormant payloads before they execute, minimizing potential data loss and recovery costs.

YARA Rule

rule ABCCryptor10byZloY
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 68 FF 64 24 F0 68 58 58 58 58 90 FF D4 50 8B 40 F2 05 B0 95 F6 95 0F 85 01 81 BB FF 68 [4] BF 00 [3] B9 00 [3] 80 37 ?? 47 39 CF 75 F8 [54] BF 00 [3] B9 00 [3] 80 37 ?? 47 39 CF 75 F8 }

condition:
		$a0
}

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 1 string patterns in its detection logic.

• Source Rule

False Positive Guidance

• Scenario: A developer or DevOps engineer manually downloads the ABCCryptor10byZloY binary (or a test build of it) to a staging or development workstation to analyze its behavior, compare it against known good samples, or test backup/restore procedures. The file remains in a temporary directory (e.g., C:\Users\dev\Downloads\) or a specific analysis folder.

  • Filter/Exclusion: Exclude paths containing \\analysis\\, \\staging\\, or \\dev\\ for user accounts with the DevTeam or SecurityOps AD group. Additionally, exclude files with the .bak or .test extension if the rule allows for extension-based filtering, or whitelist the specific hash of the known test sample.

• Scenario: An IT administrator uses a portable version of the tool on a jump host or management server to perform an emergency data recovery or encryption/decryption task on a shared network drive or local volume. The tool is copied to the C:\Tools\ or C:\Admin\ directory and executed directly.

  • Filter/Exclusion: Exclude execution from paths like C:\Tools\, C:\Admin\, or C:\Utilities\ for accounts in the LocalAdmins or ITSupport group. Ensure the exclusion is scoped to specific service accounts or admin groups to avoid over-excluding standard user paths.

• Scenario: A scheduled maintenance job or PowerShell script on a file server or backup server uses ABCCryptor10byZloY as a utility to encrypt or decrypt specific data blocks as part of a custom data lifecycle management policy. The binary is stored in a dedicated application directory, such as C:\Program Files\CustomBackup\bin\.

  • Filter/Exclusion: Whitelist the specific executable path