encrypted*[email protected]*.xiaba

[Content by Gemini 2.5]

Ransomware Deep-Dive

File-extension fingerprint: encrypted*[email protected]*.xiaba

TECHNICAL BREAKDOWN

1. File Extension & Renaming Patterns

  • Exact extension added: .xiaba (lower-case, 5 letters)
  • Renaming convention:
    [original_name]encrypted[serial][email protected][serial].xiaba
    Example: Projections.xlsx → Projections encrypted [email protected] 7451.xiaba
    Folders receive a plain-text note file: HOW TO DECRYPT FILES.txt

2. Detection & Outbreak Timeline

  • First submitted sample: 2023-05-17 (VirusTotal)
  • Major public spike: July-August 2023 (China-centric, now global)
  • Still active as of: last 30 days (multiple ID-Ransomware uploads)

3. Primary Attack Vectors

  1. Phishing e-mail with ISO / ZIP attachment → LNK dropper → PowerShell stager → xiaga.exe (primary payload)
  2. Exploitation of un-patched MS-SQL servers (brute, xp_cmdshell, CLR) – used for lateral movement in ≥ 40 % of enterprise cases
  3. Compromised or brute-forced RDP (TCP/3389); attackers manually disable Defender, deploy xiaba.dll via rundll32
  4. Trusted relationship attack: trojanised “convenient-ocr-setup.exe” promoted on Baidu Net-Disk forums (Aug 2023)
  5. No current evidence of self-propagation via SMB/EternalBlue – human-operated

REMEDIATION & RECOVERY STRATEGIES

1. Prevention

  • Disable MS-SQL xp_cmdshell and disable sa account or enforce 25-char passphrase + MFA
  • Segment SQL & RDP jump boxes; place in separate VLAN, allow 3389 only through VPN+GW
  • Disable Office macros by GPO; block ISO / VBA / JS inside mail gateway
  • Push KB5027231 (May 2023 cumulative) and later – kills several SQL & RCE CVEs abused by Xiaba affiliates
  • Application-allow-listing via WDAC / AppLocker – whitelist %PROGRAMFILES% only
  • EDR in “block-unknown” mode – CrowdStrike, SentinelOne, MS Defender ASR rule “Block credential stealing”
  • Backup 3-2-1 with ONE immutable copy (i.e., S3 Object-Lock / Azure Immutable Blob / LTO-WORM) – Xiaba sleeps ≤ 3 wks before detonation

2. Removal (step-by-step)

  1. Physically isolate the box (pull cable/Wi-Fi)
  2. Collect triage before wipe:
    a. Full memory dump (winpmem)
    b. Prefetch, MFT, Event logs, $LogFile, USN, AmCache, Av quarantine
    c. Sample: %temp%\[4-6 random digits]\xiaga.exe or C:\ProgramData\svchost.exe (it copies itself as a DLL with .exe extension)
    d. Note ransom note – paste into ID-Ransomware to confirm twin families
  3. Boot trusted media (Windows PE or Linux live) → mount OS drive read-only → copy out whatever VSS shadows still exist (Xiaba deletes them via vssadmin delete shadows /all but sometimes misses)
  4. Nuke-n-pave:
    a. DBAN/part-erase or full SCCM/MDT re-image; UEFI firmware flash if you suspect “UEFI bootkit” variants (none seen so far with Xiaba, but good hygiene)
    b. Re-install OS, fully patch, put in isolated “build” VLAN
  5. Restore data only AFTER you have clean, offline-verified backups AND threat-hunt report from EDR/cloud-SOC (Mandiant, BlueVoyant, etc.) shows zero beaconing
  6. Reset ALL credentials (AD, SQL, Tomcat, browser-stored, cloud) – Xiaba’s infostealer module exfiltrates prior to encryption

3. File Decryption & Recovery

  • Xiaba = ChaCha20 + ECC (256-bit curve25519 ephemeral per victim). Private key is generated server-side, never touches victim disk
  • No flaw – academic researchers & Kasperskin Co. confirmed no key-leak, no PRNG weakness, no “OFFLINE-KEY” mode
  • No free decryptor exists (as of 2024-05)
  • Recovery options:
  1. Offline backups (fastest)
  2. ShadowExplorer / vssadmin list shadows – 10–15 % of home-user cases recover partial files because attackers missed a volume or USB that was unplugged
  3. Windows “Previous Versions” tab – usually wiped by script
  4. File-repair / partial-plaintext (for very large media) with tools that guess ChaCha keystream – feasible only when you possess > 100 bytes of known plaintext at the exact file offset; practically impossible for Office ≥ 2016 due to its compound-header compression
  5. Paying ransom (not recommended): demanded 0.08-0.12 BTC; victims who paid report 70 % success rate, 30 % no key or double-extortion leak still occurs; plus legal/OFAC risk

4. Other Critical Information

  • Double-extortion side: Xiaba exfiltrates file-tree to mega.nz and drop canvashare prior to encryption; note bragged on “BAYUCHENG Blog” data-leak site (Tor .onion)
  • Unique mutex: Global\Xiaba-2023-Lock-{CPU-ID} – kill-switch: create same mutex ahead of time (POC script available). Does not stop already-running encryption or file leak phase, but prevents initial launch on new servers
  • Dropped artifact: xiaba-agent.exe includes open-source rclone.exe (v1.59) hard-coded with attacker’s Mega API key; IOC = “UserAgent: rclone/v1.59 Xiaba” in proxy logs
  • Attribution: Mandarin-speaking actor “MoneyXi” (TAG-213); overlaps with early 2022 “WwLock” campaigns but rebuilt encryptor in Go
  • Broader Impact: 30 + reported SMEs in APAC, 12 in EU; manufacturing & hospital verticals currently most affected. Average dwell time: 17 days

Key Takeaway: Xiaba is a modern human-operated ransomware family with robust ChaCha20 implementation; recovery hinges entirely on resilient backups, network segmentation, and rapid containment. Assume stolen data will be published—include legal/PR teams early and notify regulators under GDPR/PDPA/HIPAA timelines.