Dico

Overview

Dico (classified across antimalware research as Ransom:Win32/Dico, Trojan-Ransom.Win32.Dico, and Ransom.Dico) is a high-impact corporate crypto-ransomware family designed for rapid and thorough enterprise extortion campaigns. Typically deployed in human-operated intrusions following initial access gained via stolen remote access credentials or phishing loaders, Dico prioritizes high-value corporate servers and storage arrays. Upon execution with elevated administrator or SYSTEM privileges, Dico initiates environmental reconnaissance, verifying domain controller connectivity and enumerating active Active Directory network resources. The ransomware uses an AES-256-CBC symmetric cipher combined with an embedded RSA-2048 public master key to encrypt documents, financial spreadsheets, databases, CAD designs, and backup archives. Encrypted files are renamed with a unique extension, and ransom notes titled `README_RESTORE_FILES.txt` are created in every folder. Dico deletes Volume Shadow Copies, clears Windows security and system event logs via wevtutil, and instructs victims to negotiate extortion payment exclusively through Tor.

Known aliases

Threat reports may refer to this family under multiple names:

• Ransom:Win32/Dico
• Trojan-Ransom.Win32.Dico
• Win32/Dico
• Dico Ransomware
• Ransom.Dico

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:

• T1105: Implement network intrusion detection systems (NIDS) and host-based firewalls to block unauthorized inbound or outbound file transfers.
• T1566.001: Scan email attachments for malicious macros, scripts, or suspicious archive files.

MITRE D3FEND™ Defensive Countermeasures

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

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_DICO_T1_ARTIFACT {
    meta:
        description = "Tier 1 Primitive Artifact: Raw string matches for Dico"
        tier = "T1 - Primitive Artifact"
        confidence = "Low-Medium (Fast Triage)"
        author = "SystemHelpdesk Threat Research Desk"
        date = "2026-10-14"
    strings:
        $s1 = "dico" ascii wide nocase
        $s2 = "ransom:win32/dico" ascii wide nocase
        $s3 = "trojan-ransom.win32.dico" ascii wide nocase
        $s4 = "win32/dico" ascii wide nocase
        $s5 = "dico ransomware" ascii wide nocase
        $s6 = "ransom.dico" ascii wide nocase
    condition:
        uint16(0) == 0x5a4d and any of them
}

title: SystemHelpDesk Detection - Dico (Ransomware) Execution & Triage
id: e9f2173b-451e-59e4-9c82-49709aebf488
status: production
description: Detects execution, defense evasion, and persistence behaviors associated
  with the Dico 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/dico
- 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.t1070_001
- attack.t1083
- attack.t1135
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_DICO_T3_ATTRIBUTION {
    meta:
        description = "Tier 3 Attribution Fingerprint: Heuristic detection for Dico 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 = "dico" 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 the endpoint immediately to prevent Dico from downloading and executing its secondary payloads (e.g., ransomware).
2. Audit the Windows Task Scheduler and Registry Run keys to identify and remove the Dico persistence mechanisms.
3. Review firewall and proxy logs to identify the C2 domains Dico attempted to contact, and block them enterprise-wide.
4. Capture a live memory image (RAM dump) to extract the injected Dico modules and identify the secondary payloads.

What to Avoid

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

1. Do not close an incident simply because the initial Dico dropper was quarantined; always verify if secondary payloads were downloaded.
2. Avoid relying solely on manual file deletion, as the injected processes will likely just recreate the dropped binaries.

References & External Analysis

• Microsoft Defender Threat Encyclopedia - Ransom:Win32/Dico
• Sophos Threat Center - Ransom_Dico Analysis
• MITRE ATT&CK - Indicator Removal: Clear Windows Event Logs (T1070.001)
• Search "dico" on VirusTotal (External Analysis)
• Search "dico" on Any.Run (Sandbox Sandbox)
• Search "dico" on MalwareBazaar (Malware Samples)

Frequently Asked Questions

Related Threats (Category: Ransomware)

Explore other documented threats in the same operational category:

• Gosys
• Quireap
• Dorgam
• Gimemo
• Lowzones
• Vmpbad
• Hioles
• Wellmess

Machine-readable

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