{
  "family": "hiddentears",
  "sample_count": 2,
  "category": "ransomware",
  "description": "Ransomware:Win32/Hiddentears is a highly significant case study in malware history. It was originally released on GitHub in August 2015 by a Turkish programmer as an 'educational' open-source ransomware project. Predictably, it was immediately weaponized by low-skill threat actors ('script kiddies'), spawning hundreds of real-world ransomware variants (like MoWare, Cryptear, and KryptoLocker). It demonstrates the extreme danger of publishing destructive code, regardless of intent (`T1486`).<br><br><b>Understanding Hiddentears (Open-Source Ransomware)</b><br>To an end-user, a HiddenTears-based infection looks like standard ransomware: files are encrypted, extensions are changed (often to `.locked` or `.hiddentears`), and a text-based ransom note appears on the desktop. For an incident response team, identifying a variant as based on HiddenTears is often a relief, as the original encryption implementation contained fatal flaws that allow for free decryption.<br><br><b>Execution and Cryptographic Flaws</b><br>HiddenTears variants are typically distributed via low-effort malspam or dropped by other generic trojans. Upon execution, it scans the user's directories and uses AES-256 encryption (`T1486`) to lock specific file types. It communicates the encryption key to a C2 server (often a simple web panel) (`T1041`). Crucially, the original open-source code utilized a fundamentally flawed method for generating the AES key and Initialization Vector (IV). It used the standard `Random` class seeded with a predictable timestamp, allowing cryptographic researchers to easily brute-force the seed and reverse the encryption without paying the ransom.<br><br><b>Indicators of Compromise & Impact</b><br>The primary impact is data unavailability. Host-based IoCs include files appended with unusual extensions, the presence of ransom notes (often named `READ_IT.txt` or similar), and high CPU utilization by an unknown process during the encryption phase. A key indicator of a HiddenTears variant is often the presence of specific hardcoded strings from the original open-source project within the executable's memory.",
  "cta": "Published by the SystemHelpdesk team.",
  "aliases": [],
  "enrichment_level": "expert-seo",
  "faq": [],
  "faq_count": 0,
  "mitre_attack": [
    "T1041",
    "T1486",
    "T1059.003"
  ],
  "cisa_advisory": null,
  "last_updated": "2026-06-09",
  "mitre_attack_detail": [
    {
      "id": "T1486",
      "name": "Data Encrypted for Impact (The core ransomware payload)",
      "tactic": "Impact"
    },
    {
      "id": "T1041",
      "name": "Exfiltration Over C2 Channel (Transmitting the generated encryption key back to the attacker)",
      "tactic": "Exfiltration"
    },
    {
      "id": "T1059.003",
      "name": "Command and Scripting Interpreter: Windows Command Shell (Often used to delete shadow copies)",
      "tactic": "Execution"
    }
  ],
  "containment_steps": [
    "Immediately disconnect the infected machine from the network to prevent the ransomware from reaching network shares.",
    "Do not pay the ransom. Immediately search reputable security vendor sites (like NoMoreRansom) for a HiddenTears decryptor tool.",
    "Preserve the infected system in its current state; rebooting might destroy artifacts needed by the free decryption tools.",
    "Identify and patch the initial entry vector (often weak RDP credentials or malicious email attachments)."
  ],
  "what_to_avoid": [
    "Do not assume the data is lost forever; HiddenTears is notoriously flawed, and free decryption tools are widely available.",
    "Avoid paying the ransom; dealing with script kiddies using open-source tools rarely results in successful decryption."
  ],
  "target_industries": [
    "Global / Opportunistic"
  ],
  "motivation": "Opportunistic",
  "threat_actors": [
    "Unknown / Cybercriminal"
  ],
  "target_geographies": [
    "Global"
  ]
}