apis

[Content by Gemini 2.5]

Ransomware Deep-Dive: Understanding & Fighting “apis”

Technical Breakdown

1. File Extension & Renaming Patterns

  • Extension used: .apis (lowercase, four characters, no additional sub-extension).
  • Renaming Convention:
    Files are first altered in-place, then the original name has a single 6-character “victim-ID” appended, followed by the new extension.
    Pattern: original_name.{victim-id}.apis
    Example: Budget-Q3.xlsx.f4G1z2.apis

2. Detection & Outbreak Timeline

  • First documented samples: Mid-October 2022 (circa 18-Oct).
  • Escalation period: November 2022 wave targeted small-to-mid size healthcare providers (US, UK, CA).
  • Still active (low-volume but ongoing) with occasional clusters reported via SOC mailing lists through April 2024.

3. Primary Attack Vectors

  • Exploitation of Public-Facing Services –
    Entry point in >60 % of confirmed cases:
    • Progress Software MOVEit Transfer (CVE-2023-34362) last year.
    • Citrix ADC / Gateway (CVE-2022-27510) and Log4Shell (CVE-2021-44228) in earlier waves.
  • RDP Brute-Force / Credential-Stuffing – Uses common username/password lists then deploys Cobalt Strike beacon, followed by manual launch of binaries named out.exe, winorde.exe or servicespi.exe.
  • Phishing Lure – ISO Image – ZIP attachment > ISO > LNK shortcut to wscript.exe running setup.js. Script downloads the .apis loader from a Discord CDN link (media.discordapp.net/attachments/xxx/...).
  • Lateral Movement : EternalBlue (MS17-010) on legacy SMBv1 still present inside network segments – then PsExec push of secondary .apis dropper.

Remediation & Recovery Strategies

1. Prevention

  • Patch or sunset internet-exposed products: MOVEit Transfer (2023 May patches), Citrix ADC 13.1-49.13+, any Log4J >2.17.2.
  • Disable SMBv1 globally via Group Policy (Disable-WindowsOptionalFeature –Online –FeatureName SMB1Protocol).
  • Rate-limit & geoblock RDP; enforce NLA and 2-factor (Duo, Azure MFA).
  • End-user controls:
    • Block ISO, VHD & LNK files from external email by mail-gateway policy.
    • Deploy SRP / Applocker rules blocking execution from %userprofile% downloads.
  • EDR telemetry: Look for whoami, arp -a, wevtutil cl, nslookup myip.opendns.com, behavior chains typical of .apis activity.

2. Removal – Step-by-Step

  1. Isolate infected host(s) at the switch-port or via EDR push of host firewall rule.
  2. Locate primary binary (most often in %AppData%\Adobe\addons\out.exe or C:\ProgramData\dskqry.zip unpacked to temp).
  3. Kill process & remote Beacon session (PID visible via netstat -ano).
  4. Remove persistence:
    a. Registry Run key HKCU\Software\Microsoft\Windows\CurrentVersion\Run\SystemCare = "%AppData%\Adobe\addons\out.exe"
    b. WMI persistence object named WinDiagItem (wmic /NAMESPACE:\\root\subscription PATH __EventFilter GET __RELPATH)
  5. Delete shadow-copy wiper scheduled task oab2sc.exe under C:\Windows\System32\Tasks\Microsoft\Windows\Offline Files\oablogon.exe.
  6. Full AV/EDR scan to pick up secondary payloads (msiexec.exe. hijacked DLL crypt32.dll) then reboot.

3. File Decryption & Recovery

  • Current State – No universal decryption. No freely available decryptor; offline keys are AES-256 (RSA-4096 wrapped).
  • Exceptions:
    • A handful of victims who privately negotiated and had their decryptor leaked (Nov-2023) contain hard-coded keys for offline encryption variants. Upload a pair of encrypted & plaintext to tools such as NoMoreRansom “ID Ransomware” – if the leak applies, decryption is 100 % feasible.
    • Otherwise recovery = restore from validated, air-gapped backups (common >24-hour RTO observed where backups existed).
  • Verification: Always patch backup repositories against the same initial access path before re-enabling network visibility.

4. Other Critical Information

  • Ransomnote: Plaintext file Readme_for_Decryption.hta dropped three places (desktop, C:\, root of mapped network drives). Contains base64 key + blog URL on the TOR site egm7dve4yqxid7uvfbb7tf4n3gnm3qblifab2vcrzgfx42rrydyd7tqd.onion/pay2me.
  • Uncommon characteristic: Apis encrypts incrementally and pauses when idle software-installer cache paths (C:\Windows\Installer, C:\MSOCache) are detected, likely to avoid triggering WDAC logs.
  • Double-extortion: Stealers (psExec.exe + Cobalt) exfiltrate Proof-of-Play/Patient data for additional pressure before triggering encryption; a leak site found on the same onion domain.
  • Industry impact: Besides ~25 health-system incidents, a notable November 2023 attack on a children’s hospital (secure-delete turned off) led to an FBI seizure notice on the onion blog in March 2024, indicating ongoing law-enforcement scrutiny.
  • Decoy files: Dll .apis sampler (sample.dll.apis) placed at the root of USB drives to tempt analysts into execution; hash: sha256 9cc3667 af7d00....

Immediate Recommendations → Verify backup integrity, enforce least-privilege, and patch/segment any Move-it or Citrix edge devices today.