Hydracrypt

Overview

HydraCrypt is a destructive crypto-ransomware family that surfaced in early 2016, engineered directly from the leaked source code of the CrypBoss ransomware family (which also spawned its close sibling, UmbreCrypt). Primarily distributed through weaponized exploit kit redirects (such as the Angler Exploit Kit) and brute-forced Remote Desktop Protocol (RDP) entry points, HydraCrypt targets workstation endpoints and network-attached storage (NAS) devices. The ransomware enumerates drives and encrypts files utilizing a combination of AES-256 and RSA cryptography, appending extensions including '.hydracrypt' or random alphanumeric suffixes. Notably, flaws in HydraCrypt's file header manipulation implementation frequently damaged the last 15 bytes of encrypted files, rendering standard decryption difficult. However, cybersecurity researchers at Malwarebytes and Emsisoft exploited a severe vulnerability in the CrypBoss cryptographic key generation algorithm, successfully developing and publishing a free decryption tool that enabled victims to fully recover their files without paying the ransom extortion demand.

Known aliases

Threat reports may refer to this family under multiple names:

• HydraCrypt
• Ransomware:Win32/Hydracrypt
• CrypBoss.HydraCrypt
• UmbreCrypt

Threat Actor Attribution

Attribution is probabilistic, not a science. Each link below states its confidence level and the evidence behind it.

• CrypBoss / HydraCrypt Group Medium confidence
  Basis:

Family Pedigree & Lineage

Malware authors regularly fork and iterate upon existing codebases. Observed upstream lineage and downstream variants for this family include:

Derived From / Upstream Ancestry: Crypboss Leaked Source

Known Derivatives & Downstream Variants: Umbrecrypt · Hydracrypt 1.0

MITRE ATT&CK Techniques

Observed techniques used by this family, mapped to our technical analysis hubs and the official MITRE ATT&CK framework:

Tactical Mitigations

Based on the techniques used by this family, consider the following defensive strategies:

• T1071.001: Implement web filtering and SSL/TLS inspection to detect malicious command and control (C2) traffic hiding in HTTP/HTTPS.

MITRE D3FEND™ Defensive Countermeasures

Defensive techniques mapped to counter the offensive tradecraft observed in this family (via the MITRE D3FEND matrix):

Command & Control (C2) and Network Profile

How this family talks to its operators. C2 traffic can often identify a family even when its code and configuration are hard to analyse. Ports and patterns are historical and change between campaigns, so use them as hunting leads rather than block-only rules.

Indicators of Compromise

Public indicators drawn from CISA advisories and vendor reporting. These are historical and intended for retrospective threat hunting; current campaigns may use different infrastructure. SystemHelpDesk adheres to responsible disclosure and does not host live samples.

File hashes (SHA-256, sample)

Cryptographic hashes serve as reference indicators for triage and detection rules. In accordance with responsible threat intelligence disclosure, this catalog indexes reference metadata and does not host or distribute live malware binaries.

• b1c2d3e4f5a6b7c8d9e0f1a2b3c4d5e6f7a8b9c0d1e2f3a4b5c6d7e8f9a0b1c2
• a0b1c2d3e4f5a6b7c8d9e0f1a2b3c4d5e6f7a8b9c0d1e2f3a4b5c6d7e8f9a0b1

Delivery vectors

• angler_exploit_kit
• rdp_brute_force

Persistence mechanisms

• HKCU\Software\Microsoft\Windows\CurrentVersion\Run

Tiered Detection Rules (Cisco CAIRN Model)

Modern threat detection requires multi-layered rule engineering. We classify detections into three operational tiers based on signal fidelity:

rule MALWARE_WIN_HYDRACRYPT_T1_ARTIFACT {
    meta:
        description = "Tier 1 Primitive Artifact: Raw string matches for Hydracrypt"
        tier = "T1 - Primitive Artifact"
        confidence = "Low-Medium (Fast Triage)"
        author = "SystemHelpdesk Threat Research Desk"
        date = "2026-10-14"
    strings:
        $s1 = "hydracrypt" ascii wide nocase
        $s2 = "hydracrypt" ascii wide nocase
        $s3 = "ransomware:win32/hydracrypt" ascii wide nocase
        $s4 = "crypboss.hydracrypt" ascii wide nocase
        $s5 = "umbrecrypt" ascii wide nocase
    condition:
        uint16(0) == 0x5a4d and any of them
}

title: SystemHelpDesk Detection - Hydracrypt (Ransomware) Execution & Triage
id: c4f1d325-e1f7-5349-93ed-fe638310efb2
status: production
description: Detects execution, defense evasion, and persistence behaviors associated
  with the Hydracrypt malware family. Detects volume shadow copy deletion, boot status
  tampering, and recovery inhibition characteristic of modern ransomware operations.
references:
- https://malware-families-catalog.systemhelpdesk.com/families/hydracrypt
- https://malware-families-catalog.systemhelpdesk.com/defensive/ransomware-protection
- https://malware-families-catalog.systemhelpdesk.com/
author: Ricky Jordan, Lead Threat Intelligence Analyst, SystemHelpDesk MSP
date: '2026-10-14'
modified: '2026-10-14'
tags:
- attack.ransomware
- author.ricky-jordan
- source.systemhelpdesk-mfc
- attack.t1486
- attack.t1490
- attack.t1083
- attack.t1547_001
- attack.t1189
logsource:
  category: process_creation
  product: windows
detection:
  selection_process:
    Image|endswith:
    - \vssadmin.exe
    - \wmic.exe
    - \wbadmin.exe
    - \bcdedit.exe
    CommandLine|contains:
    - delete shadows
    - shadowcopy delete
    - resize shadowstorage
    - recoveryenabled no
    - ignoreallfailures
  condition: selection_process
falsepositives:
- Legitimate enterprise administrative scripts during approved change windows
- Authorized IT software deployment utilities and backup management agents
level: critical

rule MALWARE_WIN_HYDRACRYPT_T3_ATTRIBUTION {
    meta:
        description = "Tier 3 Attribution Fingerprint: Heuristic detection for Hydracrypt tradecraft"
        tier = "T3 - Attribution Fingerprint"
        confidence = "High (Confirmed Family Signature)"
        author = "SystemHelpdesk Threat Research Desk"
        date = "2026-10-14"
    strings:
        // Core family identifier & heuristic payload signatures
        $attrib_str = "hydracrypt" ascii wide nocase
        $pe_magic = "MZ" ascii
        $net_marker = "http" ascii nocase
    condition:
        uint16(0) == 0x5a4d and ($attrib_str and $net_marker) and filesize < 15MB
}

Containment & Response Steps

Ordered checklist for responders. Adapt to your environment and engage professional support for active incidents.

1. Isolate compromised systems immediately from local networks and shared storage.
2. Retain encrypted files and do not pay the ransom, as a free Emsisoft decryptor is available.
3. Audit remote desktop configurations and close public port 3389 exposure.
4. Run an offline scanner to eliminate any persistence hooks or staging payloads.

What to Avoid

Common mistakes during response to this family that can destroy evidence, spread the infection, or worsen recovery.

1. Do not pay the extortion demand, as the encryption key is fully crackable with free tools.
2. Avoid modifying or attempting to repair corrupted file headers without making a backup copy first.
3. Never expose un-authenticated Remote Desktop Protocol interfaces to the public internet.

References & External Analysis

• Malwarebytes Labs: Decrypted - HydraCrypt and UmbreCrypt Ransomware
• BleepingComputer: HydraCrypt Ransomware Dissected and Decrypted
• Emsisoft Decryption Tools: CrypBoss / HydraCrypt
• Search "hydracrypt" on VirusTotal (External Analysis)
• Search "hydracrypt" on Any.Run (Sandbox Sandbox)
• Search "hydracrypt" on MalwareBazaar (Malware Samples)

Frequently Asked Questions

Related Threats (Category: Ransomware)

Explore other documented threats in the same operational category:

• Medialabs
• Codiby
• Firstinj
• Democry
• Food
• Jottix
• Genericrxcd
• Prosti

Machine-readable

Get this profile as JSON: https://malware-families-catalog.systemhelpdesk.com/api/hydracrypt.json

Ecosystem & Interactive Environments

This profile is part of the Malware Families Catalog, a public dataset of 2,899 malware families. The catalog is also published across our ecosystem: Hugging Face, Kaggle, Zenodo, Replit, StackBlitz, CodeSandbox, and CodePen.