Hydracrypt

Overview

Ransomware:Win32/Hydracrypt is a destructive crypto-ransomware family designed to extort organizations by encrypting critical data and demanding payment in cryptocurrency for the decryption key. It is closely related to the UmbreCrypt ransomware family and gained notoriety for a flaw in its encryption implementation that allowed security researchers to eventually build a free decryption tool.

Understanding Hydracrypt (Ransomware)
To an end-user, a Hydracrypt infection is catastrophic. Files become inaccessible, their extensions are changed (e.g., appended with `.hydracrypt_ID_...`), and a text or HTML file drops onto the desktop demanding a ransom. For an enterprise, it represents a massive incident requiring immediate disaster recovery protocols. The attackers leverage encryption (`T1486`) to ensure data recovery is impossible without the attacker's key (or a known decryptor).

Execution and Extortion Mechanics
Hydracrypt is typically distributed via Exploit Kits (like Angler) (`T1189`) or malspam campaigns. Upon execution, the malware rapidly disables local recovery options (`T1490`) by executing `vssadmin.exe Delete Shadows /All /Quiet`. It then traverses local drives and mapped network shares, encrypting files matching specific extensions. It utilizes a flawed implementation of AES encryption, appending a unique victim ID to the file extension. Finally, it drops the ransom note (`T1491.001`), usually named `README_DECRYPT_HYDRA.txt`, providing instructions on how to pay the ransom via a Tor hidden service.

Indicators of Compromise & Impact
The impact is severe business disruption and potential data loss. Host-based IoCs include EDR alerts for rapid, mass file modifications (`T1486`), the execution of `vssadmin.exe` to destroy backups, and the presence of files with `.hydracrypt` appended to the extension. The creation of the `README_DECRYPT_HYDRA` ransom notes is a definitive indicator. Network IoCs may include the initial dropper communicating with Exploit Kit infrastructure or the ransom portal over Tor.

MITRE ATT&CK Techniques

Observed techniques used by this family, mapped to the MITRE ATT&CK framework:

Generated Detections (Boilerplate)

These YARA and Sigma rules are auto-generated based on the family name and aliases. They must be heavily tuned before deployment in a production environment.

YARA Rule

rule MALWARE_WIN_HYDRACRYPT {
    meta:
        description = "Detects Hydracrypt (ransomware)"
        author = "SystemHelpdesk Boilerplate Generator"
        date = "2026-07-06"
    strings:
        $s1 = "hydracrypt" ascii wide nocase
    condition:
        uint16(0) == 0x5a4d and any of them
}

Sigma Rule

title: Suspicious Hydracrypt Activity
id: 0a9ac016e5602843cca9b2a8c8382a89
status: experimental
description: Detects generic indicators of the hydracrypt malware family.
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|endswith:
            - '\cmd.exe'
            - '\powershell.exe'
        CommandLine|contains:
            - "*hydracrypt*"
    condition: selection
level: medium

Containment & Response Steps

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

1. IMMEDIATELY isolate the infected machine from the network (unplug the Ethernet cable) to halt the encryption of mapped network shares.
2. Do NOT pay the ransom; Hydracrypt has known flaws, and free decryption tools (like those from Emsisoft) are available.
3. Identify the initial infection vector (e.g., outdated browser plugin exploited by an EK) and patch it enterprise-wide.
4. Utilize the free decryptor tools to restore data, or restore from offline, immutable backups.

What to Avoid

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

1. Do not reboot or power off the machine immediately if a live memory capture is possible, as the encryption keys might temporarily reside in RAM.
2. Do not connect backup drives or network shares to an infected machine to 'check' the data, as the ransomware will encrypt the backups.

References & External Analysis

• Search "hydracrypt" on VirusTotal (External Analysis)

Frequently Asked Questions

Related Families (Category: ransomware)

Explore other malware families in the same category:

• Toptoo
• Jaike
• Spora
• Dishigy
• Sysupdate

Machine-readable

Get this profile as JSON: https://jordanricky1604-ship-it.github.io/malware-families-catalog/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.