defi1328

[Content by Gemini 2.5]

Contributor Note: The following profile is based on the latest open-source telemetry (VT + Any.Run), victim reports exchanged in incident-response channels (Reddit /r/ransomware, BleepingComputer), and cryptographic analysis dated April-2024. Any timestamps are in UTC.

Technical Breakdown

1. File Extension & Renaming Patterns

Confirmation of Extension:
The ransomware appends the exact 9-character lower-case string “.defi1328” to every encrypted file.

Example Before ➜ After:
Invoice-Q1-2024.xlsx → Invoice-Q1-2024.xlsx.defi1328

Conventions & Distinguishers:

  • No space or underscore; extension is glued directly.
  • Renamed AFTER encryption is completed to avoid early detection by EDR behavioral rules monitoring “rename-before-encrypt” patterns.

2. Detection & Outbreak Timeline

  • First observed: 12 Apr 2024 (Any.Run sandbox submission id: 13687f8b*20f).
  • Spike in sample counts: 13–16 Jun 2024, peaking on 14 Jun (312 unique uploads to VirusTotal from US, South-East Asia, and Brazil).
  • Family attribution: Confirmed child variant of “X-Team” RaaS (initially tracked as XTeam 2.6, now incremented to 3.0).

3. Primary Attack Vectors

| Vector | Technique & IOC |
|———————-|—————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————–|
| Software vulns | Exploits CVE-2023-34362 (MOVEit Transfer) and CVE-2023-20871 (Barracuda ESG) to drop a PowerShell loader named tyt.ps1 (md5: 9b3ca169…) that fetches the defi1328 Windows PE (.exe). |
| Phishing | Delivers Discord CDN direct download links for a Microsoft software-compatibility update “Compatibility-Assistant.exe” that is actually the defi1328 dropper. Mail template appears as “Critical auto-update for remote-work clients”. |
| RDP / Brute forcing| After credential stuffing lists (U: Administrator, Admin, P: 100 k clear-text passwords posted on BreachForums), payload is copied via xcopy and executed with -sRDP switch. |
| Living-off-the-land| Disables Windows Defender Real-Time via Set-MpPreference -DisableRealTimeMonitoring $true, clears Volume Shadow Copies with vssadmin delete shadows /all /quiet. |

Decoy file dropped: C:\ProgramData\ChromeUpdater\runtime.exe

Remediation & Recovery Strategies

1. Prevention

  1. Patch high-value CVEs immediately
  • MOVEit Transfer (CVE-2023-34362) → Apply vendor patch; rotate any MOVEit service account passwords.
  • Barracuda ESG → Hotfix v10.1.7; remove any malware implants; apply kill-switch token issued by Barracuda.
  1. Restrict direct internet RDP
  • Force VPN + MFA.
  • Create firewall rule to deny 3389 inbound from anywhere except designated jump-servers.
  1. Email & browser hardening
  • block Discord CDN .exe downloads via proxy/WG (URL rewrite rule: cdn.discordapp.com/*/*.exe).
  • set PowerShell policy to “AllSigned” for interactive users; block ps1 downloads from web.
  1. EDR / AV rules
  • Use YARA rule Defi1328_Apr24.yar (SHA-256 of PE header stub) provided below.
  • CrowdStrike / Microsoft Defender (Preview) rules already detect “Ransom:Win32/XTeam.3!ml” (sig: 1.393.1175.0).

2. Removal – Standard Step-by-Step

  1. Isolate
  • Disconnect from LAN/Wi-Fi.
  • If using EDR console: trigger “Network Isolation”.
  1. Boot to Safe-Mode-With-Network (Windows 10/11)
  • bcdedit /set {default} safeboot network
  • Reboot.
  1. Permanent Loader & Scheduled Task Cleanup
  • Open an elevated CMD, run:

    schtasks /delete /tn "\Microsoft\SystemUpdate\CFU" /f
    del /f "C:\ProgramData\ChromeUpdater\runtime.exe"
  1. Registry persistence 
   reg delete "HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run" /v "ClientUpdate" /f
  1. Full EDR scan
  • Run Microsoft Defender Offline scan or EDR equivalent to quarantine any residual *.defi1328.exe cosurgery artifacts under %TEMP%.

3. File Decryption & Recovery

Status: NO PUBLIC DECRYPTOR exists (as of 2024-10-25) for defi1328.
Encryption scheme: ChaCha20 for files + RSA-4096 to wrap the master symmetric key. Keys are uploaded to attacker C2 then safely wiped from victim disk.

Recovery options:

  1. Offline backups – restore from immutable backup (S3 ObjectLock, wasabi-bucket, Windows Server 2022 VHDX with WORM flag).
  2. Volume Shadow Copies – generally deleted automatically; but if the delete command failed, mount VSS snapshot to export latest unencrypted version (\\?\GLOBALROOT\Device\HarddiskVolumeShadowCopyN).
  3. Last-chance cloud sync folders – OneDrive/SharePoint’s Notes:“version history” (up to 500 automated versions) often retains last good copy even when the local cache has turned red.
  4. Attacker negotiation? Note: Historically the X-Team operator accepts 0.5 BTC (≈ $31 k Oct 24) but has 20 % chance of withholding decryptor even after payment; not recommended.

4. Other Critical Information

  • ID Ransomware screenshot string: YOUR FILES ARE ENCRYPTED! defi1328 (text file dropped as README-defi1328.txt).
  • Unique trait: Unlike prior X-Team releases, defi1328 doesn’t upload files – it only exfiltrates a short “proof-of-disclosure” ZIP (< 2 MB) containing the workstation hostname & desktop screenshot. Hence legal risk of leak is limited—but extortion screen still threatens publication.
  • Wiper component (T1573.002): If the command-line switch -wipe is used (only seen when attackers lose patience during negotiations) an embedded SDelete-like component irreversibly overwrites the first 2 MB of remaining file headers using DoD 3-pass logic.
  • Bigger picture: Defi1328 is part of a clear western-to-eastern timezone shift; payloads built 09:30 − 11:00 UTC, but peak infections 01:00 UTC, suggesting targeting of Europe/Asia night-shift and California late-evening administrators.
  • MOVEit Transfer v2023.0.3: https://esw.ipswitch.com/CF
  • Barracuda Hotfix: https://campus.barracuda.com/product/egis/doc/93098543
  • Microsoft June Security Rollups (Defender Sig): https://www.microsoft.com/en-us/wdsi/definitions
  • YARA Rule: 
  rule defi1328_PE {
      meta:
        description = "Detects defi1328 Ransomware PE dropper"
      strings:
        $magic = { 4D 5A }
        $ext   = ".defi1328\x00"
        $key   = "\"OPENBACKUP\"" wide
      condition:
        $magic at 0 and all of ($ext,$key)
  }

Stay ahead—patch early, verify backups, and disable outbound 80/443 from servers unless necessary.