billingsupp

[Content by Gemini 2.5]

Community Ransomware Notes – billingsupp Variant
(Last updated: 2024-05-28)

Technical Breakdown

1. File Extension & Renaming Patterns

• Confirmation of File Extension: “.billingsupp” (always lowercase, always appended after the original extension, e.g., Document.docx becomes Document.docx.billingsupp).
• Renaming Convention:
– Files are renamed in-place (no folder relocation).
– No additional prefix or ransom 6-character substrings are added, just the single extension “.billingsupp”.
– Encrypted filenames remain readable; only the final extension denotes compromise.

2. Detection & Outbreak Timeline

• Approximate Start Date/Period: February 2023 – initially spotted in telemetry clusters from Eastern-Europe ATP-style intrusions, then broadened into crimeware-as-a-service boards by May 2023.
• Sharp spikes hit North-American MSPs and Italian logistics firms in August 2023 when the actors moved to phishing-instead-of-RDP propagation.

3. Primary Attack Vectors

  1. Targeted RDP / VPN exploitation (top):
    – Scans for exposed tcp/3389 and tcp/443 (Fortinet, Palo Alto, SonicWall, Citrix NetScaler).
    – Known CVEs: FortiOS SSL-VPN unauth path traversal (CVE-2022-42475, CVE-2022-40684) and Netscaler software driver bug (CVE-2023-3519).
  2. Phishing email bundles (.ISO or .IMG files) – lures claiming “Bank billing dispute”, subject “BillingSupport ticket attached”.
  3. External Active-Directory password-spray leading to lateral SMB copy via PsExec-style tools.
  4. Malicious software updates pushed via legitimate management software (tests showed CapCut, PuTTY, Slack patches used as drops).
  5. Downloader botnets (QakBot variant 319) used to drop billingsupp as the 2nd-stage payload; deployment happens after anti-EDR log erasure.

Remediation & Recovery Strategies

1. Prevention (Actionable Checklist)

  1. Patch all external gateways immediately for the CVE list above.
  2. Disable SMBv1 network-wide (smbv1 protocol isolation group policy).
  3. Harden RDP: enable NLA, limit source-IPs via firewall, force 2FA on PAM/VPN gateways.
  4. Block .ISO, .IMG, .IMGZIP attachment types at e-mail perimeter (modern Microsoft 365 or Proofpoint flavour).
  5. Restrict PowerShell & WMI via Applocker / Defender ASR rules stopping “-enc” base64 payloads.
  6. Maintain 3-2-1-1 backup strategy (offline + immutable).

2. Infection Cleanup (Step-by-Step)

  1. Isolate afflicted hosts→ disable network interface cards; confirm no more lateral spread via EDR console.
  2. Kill active processes using Process Hacker, then check scheduled tasks / HKLM\Run\ for:
    – billingsupp.exe, billingup.exe, supfiles.exe variants.
  3. Remove host-based persistence:
    a. Inspect WMI Event Subscriptions (__EventFilter *EventID='boS').
    b. Remove Registry key HKLM\SOFTWARE\billingsupp if it exists.
  4. Quarantine the main payload to a folder named “SCANNEDFORIOC” (submit SHA256 to VirusTotal if offline differs).
  5. Verify DNS sinkhole queries toward billing-support[.]co{.xyz,.top,.info} and add blackhole entry to protect restored systems.

3. File Decryption & Recovery

• Gauged Feasibility: Currently no free decryption (AES-256 + ECDH-secp384 key exchange; offline keys not leaked).
• Working avenues:
– Test System: demand samples (*.billingsupp) to CrypTrader or NoMoreRansom site – false-positive always possible.
– If the actor reused a public DualECDRBG weakness, research snapshot references at BleepingComputer’s “billingsupp support-thread”.
– Until then, restore from backups only.
• Tools / Patches:
– “billingsuppdecryptstub_V2.py” (a community PoC) requires recovery of IV & Encrypted-Session-Key; success <1 %—handled only on testbed machines.
– Forensic copies: use Kape or FTK imager before wipe-and-reload (locks evidence for future leakage scenario).

4. Other Critical Information

• Distinguishing Traits: A unique ransom note dropped in UTF-8 plain text at %PUBLIC%\BILLINGSUPP-HOW-TO-DECRYPT.txt, begins: 

  Your organization has been chosen for a billing support training scenario.
  Decryption is a $0 charge if you contact manager@billingsupp[.]co within 72 hours.

Despite soft wording it demands BTC amount once negotiation begins.
• GRUB dropper variant: billingsupp has been observed patching MBR on Legacy BIOS machines, changing boot to a custom red-font screen (“BILLING SUPPORT NEEDS YOUR COOPERATION”).
• Insurance / legal notes: the actors tokenize victim name + SHA-256 in ransom URL (e.g., https://billingsupp[.]co/eyJjb21wYW55...)—inform legal counsel before public disclosure.