Hiddentear

Overview

Ransom:Win32/Hiddentear is a highly significant ransomware family in cybersecurity history. Originally developed by a Turkish researcher in 2015 and released on GitHub as an 'open-source educational project', HiddenTear was intended to demonstrate how ransomware works. Predictably, it was immediately co-opted by script kiddies and low-tier cybercriminals, who slightly modified the source code to spawn hundreds of real-world ransomware variants, causing widespread damage.

Understanding HiddenTear
To a victim, a HiddenTear infection is indistinguishable from top-tier ransomware; their files are encrypted, a unique extension (e.g., `.locked`) is appended, and a ransom note demands Bitcoin. For a security analyst, a HiddenTear detection often indicates a less sophisticated adversary. Because the original source code was flawed—specifically, the random number generator used for the encryption keys was extremely weak—files encrypted by many early HiddenTear variants can actually be decrypted for free using publicly available tools.

Execution and Encryption Mechanics
Because the source code is public, the distribution vector varies wildly, ranging from spam emails (`T1566.001`) to malicious Discord links (`T1189`). Upon execution (`T1204.002`), the malware typically establishes persistence by dropping a copy of itself in the `%AppData%` or `%LocalAppData%` directory and creating a Registry Run key (`T1547.001`). The core encryption routine targets a hardcoded list of file extensions (documents, images, databases) using AES encryption (`T1486`). In the original code, the encryption key was sent in plaintext to a web server via an HTTP GET request (`T1041`). It then drops a simple text file (`READ_IT.txt`) on the desktop detailing the ransom demand.

Indicators of Compromise & Impact
The impact is significant data loss and disruption. The primary IoC is the sudden renaming of files to include anomalous extensions (which vary wildly depending on the script kiddie who compiled it) and the appearance of the ransom note. Network analysts might observe an HTTP GET request containing a string of characters (the AES key) being sent to a suspicious, often free-hosting, web domain. Static analysis of the executable will often reveal it is compiled in .NET and heavily resembles the public GitHub repository.

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

Sigma Rule

title: Suspicious Hiddentear Activity
id: 0f4dc8104e39212a06e8604b6de52354
status: experimental
description: Detects generic indicators of the hiddentear malware family.
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|endswith:
            - '\cmd.exe'
            - '\powershell.exe'
        CommandLine|contains:
            - "*hiddentear*"
    condition: selection
level: medium

Containment & Response Steps

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

1. Instantly isolate the infected endpoint from the network to halt the encryption process, specifically protecting mapped network shares.
2. Do NOT reboot the machine immediately; capture a live memory dump (RAM) first, as poorly coded variants often leave the AES key in memory.
3. Crucially, identify the specific variant of HiddenTear (based on the extension and ransom note) and check 'NoMoreRansom.org'; a vast majority of these variants have free decryption tools available.
4. If no decryptor is available, restore the affected systems from secure, offline backups.

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 ransom. HiddenTear operators are often inexperienced script kiddies who frequently lose the C2 infrastructure or the keys, meaning paying rarely results in file recovery.
2. Avoid assuming the encryption is unbreakable; the cryptographic flaws in the original source code persist in many wild variants.

References & External Analysis

• Search "hiddentear" on VirusTotal (External Analysis)

Frequently Asked Questions

Related Families (Category: ransomware)

Explore other malware families in the same category:

• Sage
• Lurk
• Zilix
• Chinbo
• Azden

Machine-readable

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