district

[Content by Gemini 2.5]

District Ransomware Community Reference Guide

Technical Breakdown

1. File Extension & Renaming Patterns

Primary Extension: .district
Renaming Convention:

  • Victim files are base-encrypted with AES-256 + RSA-4096, then renamed as:
    <original_filename>.<original_extension>.id-XXXXXXXX.[<attacker_mail>].district
  • Where:
  • XXXXXXXX is an 8-character hexadecimal Victim-ID derived from the system MAC address.
  • [<attacker_mail>] is a contact e-mail that differs across campaigns (historically: [email protected], [email protected], [email protected]).

2. Detection & Outbreak Timeline

| Date | Event |
|——|——-|
| Early Feb 2023 | First telemetry hits from hybrid-analysis sandboxes. |
| Mid Mar 2023 | Mass-email campaigns (ISO & ZIP lures) observed in North America. |
| Late Apr 2023 | Linux/ESXi ELF variant drops targeting VMware hypervisors (.district appended to .vmdk, .vmx). |
| Aug 2023 – Present | Periodic spikes aligned with ProxyNotShell (CVE-2023-23397) and Citrix Bleed (CVE-2023-4966) exploitation waves. |

3. Primary Attack Vectors

  1. Phishing & Social Engineering
  • Attachments: password-protected ZIP → ISO → LNK → PowerShell downloader.
  • Themes: fake invoices, scannable QR-code spam, fake US-CERT/FBI alerts.
  1. Exploitation of Public-Facing Applications
  • ProxyNotShell (Exchange Server) – to drop ASPX webshell that fetches district.exe.
  • Citrix Bleed (NetScaler ADC) – for lateral movement and deployment of Linux ESXi lockers.
  • Confluence OGNL (CVE-2022-26134) & Log4Shell (CVE-2021-44228) seen in earlier forks.
  1. Remote Desktop Protocol (RDP)
  • Brute-forced or purchased “initial access” credentials → manual deployment via stolen RMM tools (AnyDesk, RustDesk).
  1. Living-off-the-Land (LotL) Techniques
  • Uses certutil, powershell, and vssadmin delete shadows /all /quiet for evasion.

Remediation & Recovery Strategies

1. Prevention

  • Patch & Harden:

  • Apply March 2023 Exchange cumulative update (KB5023307).

  • Patch Citrix ADC ≥ 13.1-49.13 (or Netscaler 14.1-8.50) against BLEED.

  • Disable SMBv1, disable unused RDP externally, enforce NLA + lockout policies.

  • Perimeter & Endpoint Controls:

  • Impose “block-all / allow-some” macro & ISO execution via Group Policy.

  • Enable Windows ASR rules: Block credential stealing from LSASS, Block process-creation from Office.

  • Conditional-Access MFA for all RDP and VPN endpoints (prefer phishing-resistant FIDO2 keys).

  • Immutable Backups:

  • Deploy 3-2-1 rule: 3 copies, 2 different media, 1 offline (air-gapped).

  • Time-delayed cloud Write-Once-Read-Many (WORM) buckets with ≥ 30 days immutability.

2. Removal (Step-by-Step)

  1. Isolate
  • Disconnect from LAN/Wi-Fi, or shut down VM at hypervisor level.
  1. Identify & Kill Malicious Processes
  • Look for randomly-named .exe in %APPDATA%\Microsoft\, %TEMP%\ or /tmp/.district.
  • wmic process where "name='random.exe'" delete (Windows) or kill -9 <PID> (Linux).
  1. Delete Persistence
  • Windows: remove Run keys, scheduled tasks named “WindowsHelper”, “SysUpdate”.
  • Linux: purge systemd service files in /etc/systemd/system/district.service.
  1. Quarantine Files
  • Move quarantined samples to offline media for forensics.
  1. Run AV / EDR Scan
  • Use updated signatures (CrowdStrike, SentinelOne, Bitdefender all detect as知彼).
  1. Reboot & Validate
  • Boot into Safe Mode (Windows) or single-user mode (Linux) to confirm the ransomware process is gone.

3. File Decryption & Recovery

  • Decryptors?
  • No public decryption; District uses strong RSA-4096 with per-victim key pairs.
  • A flaw in earlier March 2023 samples leaked AES keys under specific heap-spray conditions—check NoMoreRansom’s decryptdistrictv1.exe(valid for IDs beginning with “9a4f3b1c” only).
  • Shadow Copies & Volume Images
  • Run vssadmin list shadows & rclone sync or Windows File History if not purged.
  • Linux / ESXi VM Snapshots
  • Check vSphere Datastore for immutable snapshots (*.vmsn) created by Veeam or VMware SRM.

4. Other Critical Information

  • Unique Characteristics

  • Dual-extortion: threatens data auction on MarketDistrict leaks site.

  • Chooses encryption method based on CPU core count – machines with ≤ 4 cores skip full disk encryption to reduce detectable I/O spikes.

  • Written in Go with user-mode NTFS driver (special handling of ReFS & BitLocker volumes).

  • Wider Impact & IOCs

  • Globally 370+ known victims (per MarketDistrict leak blog roll).

  • Primary verticals hit: Healthcare (25 %), Manufacturing (22 %), Local Governments (15 %).

  • Network Signatures

    • DNS beacons: districtc2.top, distlogin.net.
    • Mutex strings: DistrictMutex12345, Global\KeepMeSafe.

  • YARA Rule (truncated)
    yaml
    rule DistrictLocker {
    strings:
    $xor_key = { 4D 69 73 73 69 6F 6E } // "Mission"
    $marker = ".id-" ascii // Victim-ID prefix
    condition:
    uint16(0) == 0x5A4D and // PE start
    2 of ($*)
    }

Use this guide as a living document—re-verify patches and latest decryptor availability via NoMoreRansom.org before any recovery attempts. Stay vigilant!