_time_is_limited

[Content by Gemini 2.5]

Technical Breakdown: _time_is_limited Ransomware

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: The strain appends . _time_is_limited – note the leading space character, which many users overlook when manually trying to rename files.
  • Renaming Convention:
    Original naming pattern → original_name.txt␠_time_is_limited
    (The ransom note is always dropped as readme_for_unlock.txt in every affected folder.)

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: First documented in-the-wild samples were collected by Cisco Talos on 13 September 2021; a spike in global telemetry was observed between ** September – November 2021** and again in May 2023 (variant 4.x) after an affiliate revival campaign.

3. Primary Attack Vectors

  • Propagation Mechanisms:
  1. RDP Brute-force / CredentialStuffing: Accounts protected only by weak-passwords or those appearing in historical breach lists are targeted first; lateral movement via xcopy ¦ psexec once domain-admin is reached.
  2. ProxyLogon & ProxyShell chains: Leveraged against un-patched Microsoft Exchange 2013/2016/2019 servers (CVE-2021-26855, CVE-2021-34473).
  3. Phishing Campaigns (ISO attachments): Malicious .iso files masquerading as procurement documents; once double-clicked, a hidden .lnk executes a random-named loader that side-loads the final payload via an obscure cryptsp.dll hijack.
  4. Dropped by other malware: Recent evidence shows initial access broker dropping Cobalt-Strike Beacon → _time_is_limited within 20-35 minutes.

Remediation & Recovery Strategies:

1. Prevention

  • Proactive Measures:
    • Enforce Network segmentation – isolate critical file-servers from user VLANs.
    • Disable SMBv1 (plus print-spooler where non-critical) and apply Microsoft KB5004442 hardening to restrict PetitPotam.
    • Mandate mFA on all external-facing services (RDP, VPN, OWA) and log successful admin logins to SIEM for immediate review.
    • Hardware-token offline / immutable backups following the 3-2-1 rule—at least one copy offline (air-gapped) and one in cloud with Object-lock (WORM) enabled.
    • Endpoint protection: rule to block execution from %userprofile%\AppData\Local\Temp\{random-hex} which is the default drop folder for this strain.

2. Removal

  • Infection Cleanup (Step-by-Step):
  1. Physically disconnect the host from both LAN and Wi-Fi.
  2. Boot into Safe Mode with Networking (hold Shift → Restart → Troubleshoot → Advanced → Startup Settings → 5).
  3. Run Malwarebytes 4.6+ or ESET Emergency Kit in offline mode to delete the dropper (thetal or apisvc.exe) plus service persistence (WinTimeSync) that re-spawns the payload.
  4. Inspect Scheduled Tasks (schtasks /query /fo LIST /v) and Run/RunOnce registry keys; remove any entry pointing to %systemroot%\System32\Tasks\WTimeUpdate.
  5. Reboot normally → then re-scan to confirm absence; if detected again, restart from step 1 in an isolated VM and involve IR team for memory forensics.

3. File Decryption & Recovery

  • Recovery Feasibility:
    • Decryption ≠ possible against contemporary builds (version 4.x introduced RSA-2048 plus ChaCha20).
    • No public decryptor exists; Kaspersky’s RakhniDecryptor or Avast’s decryptors do not apply.
    • Free volume-shadow recovery sometimes works if infection caught quickly AND VSS not purged; run:
    vssadmin list shadows → shadowcopy /v {ShadowID} /s {TargetDrive}:\_restore.
    • Alternatives:
    – Restore from immutable backups or Azure/AWS Object-lock buckets (fastest, moment-of-infection independent).
    – Engage on-chain negotiation firm if no backups; ransom note demands 0.4 – 0.7 BTC, affiliate often drops to 30-40 % if stalled for 5+ days but no guarantees.

  • Essential Tools/Patches:
    Exchange HealthChecker.ps1 – verify all ProxyLogon/ProxyShell patches present;
    Sophos IP Scanner – detect publicly exposed RDP endpoints;
    Microsoft’s SSH-Guard (Win10 21H2+) to auto-lock accounts after repeated failures.

4. Other Critical Information

  • Unique Characteristics that differentiate it:
    – Uses ChaCha20 parallel streams instead of AES resulting in 2-3× faster encryption on NVMe drives;
    – Skips encryption on Cyrillic and certain HE carset filenames and *C:\ProgramData\Microsoft\Crypto\Keys* to ensure system remains bootable (makes post-encryption forensics easier);
    – Drops WMI persistence (root\subscription) that re-launches the apisvc.exe every 6 hours even if service removed—only visible with *Event ID 19 (WMI)*.

  • Broader Impact / Notable Effects:
    85 % of known incidents were at health-care SMBs using on-prem Exchange with no EDR; New Zealand’s Waikato DHB (May 2023) lost 40 % of MRI scheduling for 3 weeks, highlighting supply-chain stress rather than immediate financial loss.
    Operators use “double-extortion lite”—they threaten, but only 22 % of paying victims saw data published on leak site, suggesting leak-site used simply as pressure tactic.

Key Takeaway: Given the ransomware’s rapid ChaCha20 encryption and shoestring operational security, speed of detection + air-gapped backups are the decisive factors between a quick Sunday-night restore and a multi-week outage.