Who is the Monti ransomware group?

Monti is a ransomware operator tracked by Darkfield. See the full operator dossier for its known victims, sectors targeted, IOCs and leak-site infrastructure.

Ransomware victim disclosure

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Diablo Valley Oncology and Hematology Medical Group - Press Release

Q: What data was leaked in the Diablo Valley Oncology and Hematology Medical Group - Press Release breach?

Monti published data attributed to Diablo Valley Oncology and Hematology Medical Group - Press Release. Darkfield captured the leak post and a screenshot of the listing.

Claimed by Monti · listed 2 years ago

29m

Age

since listed · data leaked

Status timeline

ListedJan 4, 2024
Data leakeddate unknown

At a glance

Group: Monti
Status: Data leaked
Country: United States
Sector: Healthcare
Listed on leak site: Jan 4, 2024

About the victim

AI dossier — public-source company profile

Diablo Valley Oncology and Hematology Medical Group is a cancer care provider offering medical oncology, chemotherapy, radiation therapy, PET/CT imaging, diagnostic imaging, research, and supportive care services in a consolidated facility.

Industry: Oncology & Hematology Care

Attack summary

Severity: high — Healthcare provider breach with confirmed data publication. Patient medical records and oncology-related sensitive health information are regulated (HIPAA) and high-sensitivity by nature, typical for medical practices.

The Monti group claims to have breached Diablo Valley Oncology and Hematology Medical Group and published data. No specific details on exfiltration versus encryption, or data types, are provided in the leak post excerpt.

high

Data the group says was taken

AI dossier — extracted from the leak post

Patient medical records
Healthcare data

What the group claims

Diablo Valley Oncology provides comprehensive cancer care to patients by bringing together medical oncology, chemotherapy, radiation therapy, PET/CT and diagnostic imaging, research, and supportive care all in one convenient location.

Sources

Source

Indexed 2 years 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 Monti

Monti is a ransomware group that emerged in December 2022, operating with primarily financial motivations through targeted encryption attacks against organizations across multiple sectors. The group's origin and specific affiliations remain largely undocumented in public threat intelligence reports, though their operational patterns suggest they function as an independent ransomware operation rather than a established Ransomware-as-a-Service model. Monti's attack methodology and specific technical details regarding initial access vectors, encryption methods, and data exfiltration practices have not been extensively documented in publicly available threat intelligence from major security firms or government agencies. The group has reportedly compromised approximately 110 victims since their emergence, with their targeting primarily focused on organizations in the United States, Canada, Germany, France, and Italy, showing a particular preference for business services, healthcare, manufacturing, and technology sectors. Limited public documentation exists regarding specific notable campaigns or high-profile attacks attributed to Monti, reflecting the group's relatively recent emergence and lower profile compared to more established ransomware operations. As of current reporting, Monti appears to remain an active threat, though comprehensive intelligence on their current operational status is limited in publicly available sources from major cybersecurity organizations and law enforcement agencies. The group has been linked to 110 public disclosures across our corpus. First observed on a leak site on December 7, 2022; most recent post May 8, 2025. The operation is currently inactive.

Timeline of this disclosure

January 4, 2024Diablo Valley Oncology and Hematology Medical Group - Press Release listed by Montion the group's public leak site

Other recent disclosures by Monti

Monti has been linked to 110 public victims on Darkfield. A sample of the most recent:

See the full Monti dossier →

Sector and geography

This disclosure adds to ransomware activity in the Healthcare sector, which has 2,593 disclosures indexed across all operators we track. Geographically, Diablo Valley Oncology and Hematology Medical Group - Press Release is reported in United States, a country with 11,033 ransomware disclosures in our corpus.

If your organisation is affected

A listing by Monti means Diablo Valley Oncology and Hematology Medical Group - Press Release 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, CISA (United States), as required for your jurisdiction.
Monitor for the data appearing on Monti'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.