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Tab Service

Claimed by Coinbasecartel · listed 2 months ago

2m
Age
since listed · data leaked

Status timeline

  1. ListedMay 11, 2026
  2. Data leakeddate unknown

At a glance

Group
Coinbasecartel
Status
Data leaked
Country
Germany
Sector
Business Services
Listed on leak site
May 11, 2026

About the victim

AI dossier — public-source company profile

Tab Service Company is a US-headquartered back-office outsourcing firm with over 65 years of operation, serving 2,500+ clients across regulated industries including healthcare, higher education, fintech, banking, and legal. The company provides tax form processing and e-filing (1099, 1098-T), document scanning, print and mail, data entry, digital mailroom, and survey services. It holds SOC 2 certification, HIPAA compliance, and is an IRS Authorized E-File Provider, indicating it handles sensitive regulated data at scale.

Industry
Back-Office Outsourcing & Document Processing Services
Founded
1959

Attack summary

Severity: critical — Tab Service processes regulated data at scale for thousands of clients across healthcare, fintech, banking, higher education, and legal sectors — including HIPAA-covered health data, IRS tax documents, and financial records. A confirmed data publication event at this type of organization implies likely exfiltration of sensitive PII and regulated financial/medical records affecting potentially millions of end-users across 2,500+ client organizations.

The coinbasecartel ransomware group claims to have compromised Tab Service and has published data (disclosed status: data_published); however, the leak post contains no substantive detail about the nature of the attack, whether encryption or exfiltration occurred, or what specific data was taken.

critical

Data the group says was taken

AI dossier — extracted from the leak post
  • Tax documents (1099, 1098-T forms)
  • Client records from regulated industries
  • Healthcare data (HIPAA-covered)
  • Financial/banking records
  • Scanned paper documents
  • Survey data
  • Physical mail contents (digital mailroom)
  • Data entry records

Original description

AI-summarised, not from the leak post

N/A

The leak post

captured from the group's site
System Breach • Coinbasecartel We are looking for new partners/insiders. Send us a message to dicuss We are looking for new partners/insiders. Send us a message to dicuss CRITICAL ANNOUNCEMENTS × Contact Update We have changed our contact method. We now exclusively use qTox Messenger for all communications. SimpleX and Session have been discontinued. Our Tox ID: A7580331D4D16453CCE86D7ADFBCF0CEED0D0D1AEA8F4DBEEBCA9E3B46308F260DE9B41BD838 TO APTIM You may have noticed the sudden, heavy silence. The corporate VPNs are dead. We have been the silent architects of your network for the past three weeks. While your "elite" investigators from Mandiant sat in your logs, we sat directly beside them burning through over a hundred of your corporate identities like disposable tools. we have had your entire network and internal protocols. HOW LONG WILL YOU KEEP YOUR THOUSANDS OF FIELD WORKERS LOCKED OUT? We have successfully exfiltrated the most sensitive engineering data held by any firm in your sectors We hold the complete Navisworks 3D models, P&ID diagrams, and maintenance logic for your major energy plants. This includes the granular Honeywell DCS controller logic. We know…

Sources

Source

Indexed 2 months ago

This page surfaces a public ransomware disclosure indexed by Darkfield. Original posts come from the operator's own leak site; we cross-check against ransomware.live, RansomLook and RansomWatch where applicable. Share this URL freely.

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Disclosure context

About coinbasecartel

CoinbaseCartel is a ransomware group that emerged in September 2025 with financially motivated operations targeting organizations across multiple sectors and geographic regions. The group has demonstrated significant activity in a short timeframe, compromising at least 102 known victims primarily across the United States, United Arab Emirates, Germany, Canada, and Brazil. Their targeting patterns show a preference for technology companies, financial services organizations, manufacturing entities, and consumer services businesses, suggesting an opportunistic approach focused on organizations likely to have both valuable data and the financial resources to pay ransoms. Given the group's recent emergence and limited public documentation from established threat intelligence sources, details regarding their specific attack methodologies, infrastructure, and organizational structure remain largely unconfirmed by major cybersecurity firms or law enforcement agencies. The group appears to maintain active operations as of late 2025, though comprehensive analysis of their tactics, techniques, and procedures awaits further investigation and reporting by established threat intelligence organizations. The group has been linked to 188 public disclosures across our corpus. First observed on a leak site on September 15, 2025; most recent post July 14, 2026. The operation is currently active.

Also tracked as: coinbase cartel.

Timeline of this disclosure

  • May 11, 2026Tab Service listed by coinbasecartelon the group's public leak site

Other recent disclosures by coinbasecartel

coinbasecartel has been linked to 188 public victims on Darkfield. A sample of the most recent:

See the full coinbasecartel dossier →

Sector and geography

This disclosure adds to ransomware activity in the Business Services sector, which has 3,796 disclosures indexed across all operators we track. Geographically, Tab Service is reported in Germany, a country with 379 ransomware disclosures in our corpus.

If your organisation is affected

A listing by coinbasecartel means Tab Service appeared on a ransomware extortion site and data attributed to it has been published. If this is your organisation, or a supplier you depend on, the priority is to confirm the intrusion and contain it before the window to act closes.

  • Engage your incident-response team and preserve forensic evidence before remediating — do not wipe affected systems first.
  • Force a password reset and revoke active sessions for exposed accounts; rotate any credentials, API keys or certificates that may have been in the stolen data.
  • Assess regulatory notification duties (GDPR, NIS2, sector regulators) — many carry a 72-hour reporting clock from awareness.
  • Report the incident to your national CERT, CERT-Bund (Germany), as required for your jurisdiction.
  • Monitor for the data appearing on coinbasecartel's leak site and across paste and breach channels, and brief downstream partners who may be exposed through you.

How we know this. Darkfield monitors public ransomware leak sites continuously, archiving every new disclosure and the data later released against the victim. Each entry on this page is sourced from the operator's own publication and cross-checked against complementary OSINT feeds (RansomLook, ransomware.live, RansomWatch). We do not collect or host stolen data — only the metadata, timestamps and screenshots needed to make the public disclosure searchable and accountable. Records here are corrected when the original post is edited, retracted, or merged with another disclosure.