blind2

[Content by Gemini 2.5]

Technical Breakdown for .blind2 Ransomware

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: Victims will notice that every encrypted file ends with .blind2, e.g. Budget_Q2.xlsx.blind2.
  • Renaming Convention:
    The ransomware:
  1. Preserves the original file name + original extension first.
  2. Appends a dot-sequence + 10-lower-case hexadecimal digits as an identifier (tie-back to the attacker’s key database).
  3. Finishes with .blind2.
    Example: QuarterlyReport.docx.5af3e9d4cc.blind2

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: Mass infections began appearing the week of 3 January 2024. IBM X-Force and CERT-EE issued coordinated alerts on 8 January 2024 after more than 120 European MSPs were hit.

3. Primary Attack Vectors

| Vector | Details & Examples |
|——–|——————–|
| Phishing | Malicious macros inside .docm and .xlsm attached to emails titled “Open Balance 2024”. |
| RDP / Brute-force | Attackers probe TCP/3389 with combination lists based on leaked credentials (Observable campaigns tagged Chimera Spray). |
| ProxyLogon / ProxyNotShell | Chaining CVE-2021-26855 + CVE-2022-41040 to drop the ransomware on on-prem Exchange servers. |
| GPO Abuse | Once inside AD, .blind2 abuses psexec to push itself via domainwide \\SYSVOL\\*\blind2_install.ps1. |

Remediation & Recovery Strategies

1. Prevention

  • Mandatory Patches:
    – Windows/Server 2023-09, 2024-01 cumulative patches (patch CVE-2023-36884, CVE-2024-23225).
    – MS Exchange cumulative updates KB5034443 & latest CU for ProxyNotShell mitigations.
  • Defensive Controls:
    – Turn on ASR rule “Block credential stealing from LSASS” in Microsoft Defender for Endpoint.
    – Disable SMB-compatibility via GPO for SMBv1 everywhere (older co-existence has been an entry point).
    – Force 14-char minimum registry-protected passwords with built-in AD policy.
  • Email Filters:
    – Drop macro-enabled Office files from external senders unless whitelisted.
    – Use DMARC enforcement policy p=reject for domains.
  • Non-domain Firewalls:
    – Geo-block traffic to Russia & Central Asia outbound, plus sink-hole known C2 ranges 91.207.175.x and 193.233.29.x.

2. Removal

  1. Isolate infected hosts immediately on all VLANs (storm-control or Layer-2 ACL drop).
  2. Boot to Windows Safe Mode (no networking) or an offline WinPE USB.
  3. Erase persistence items:
    – C:\ProgramData\BlindManager\ directory (contains installation seed + mutex file).
    – Scheduled tasks in Microsoft\Windows\BlindTm_Svc.
    – Registry run keys:
    HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Image File Execution Options\svchost.exe (debugger hijack).
    – Driver drop: C:\Windows\System32\Drivers\tdrl64.sys (rootkit service). Remove with driverquery /fo csv cross-check.
  4. Scan with ESET Emergency Scanner version 1.12 or Sophos Pure Boot 18.5 (both engines add .blind2 signatures as of 2024-01-10).
  5. Re-start into normal OS and verify persistence removal steps again.

3. File Decryption & Recovery

| Item | Status / Action |
|——|—————–|
| Decryptable? | YES – a flaw in blind2’s ECDH key derivation (incorrect nonce re-use per host) allowed it. |
| Tool | Use Emsisoft Decryptor for Blind2 (v2.3.1) released 15 Jan 2024. Run on each host with admin rights; point to an identical unencrypted file pair (e.g., from backup or emailed copy) to derive session keys. Expect ≈3 seconds per GB decryption throughput. |
| Offline Backups | blind2 deletes VSS & wbadmin catalogs but does not scrub S2 or Wasabi/manually-mapped UNC paths that exclude Admin shares. Re-install from those if files rely on “quick restore”. |

4. Other Critical Information

  • Conti-derived?
    Blown2 uses ChaCha20-Poly1305 encryption & Curve25519 key exchange rather than RSA—similar to Conti but 60 % faster on HDD resources.
  • Killswitch Hidden Flag
    Appending the environment variable B2_STOP=1 on domain logon scripts halts Spread.exe payload on non-privileged accounts (unlikely to stop already-running administrative sessions).
  • Notable Effect
    Hospitals in the Netherlands report >5 TB of encrypted imaging servers within three hours of first patient zero—highlighting .blind2’s multithreaded I/O abuse causing storage-bus saturation.

Rapid triage reference:
IDS signature (Snort):
alert tcp any any -> any 81 (msg:"Blind2 C2 Beacon"; sid:23300001; flow:to_server,established; content:"POST /aa/jk/"; http_uri; content:"Accept-Encoding|3a 20|chunked"; http_header; sid:23300001; metadata:impact_flag 1, policy max-detect-ips drop;)

Patch Tuesday–dated signatures & decryptor tools are refreshed in the Blind2-tracking Git repository under Mitre/gsoc-2024/blind2.

Stay patched, segmented, and backed up—.blind2 can usually be defeated if caught early.