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Houghton Mifflin Harcourt

listed as HMH (hmhco.com) · Claimed by Hunters International · listed 9 months ago

9m
Age
since listed · data leaked

Status timeline

  1. ListedOct 3, 2025
  2. Data leakeddate unknown

At a glance

Group
Hunters International
Status
Data leaked
Country
United States
Sector
Education
Listed on leak site
Oct 3, 2025

About the victim

AI dossier — public-source company profile

Houghton Mifflin Harcourt (HMH) is a major U.S.-based K-12 learning company headquartered in Boston, Massachusetts, providing curriculum, instructional technology, and assessment products to schools in over 150 countries. Their portfolio includes core literacy and math curricula (e.g., Into Reading, Go Math!), supplemental programs, and digital learning platforms. HMH also publishes trade, reference, and children's books.

Industry
K-12 Educational Publishing & Instructional Technology
Address
125 High Street, Boston, MA 02110, United States
Employees
5001-10000
Founded
1832

Attack summary

Severity: high — Data has been published by the threat actor against a major K-12 educational publisher that handles student data across schools in 150+ countries. Exfiltration of student and institutional data at this scale constitutes significant regulated data exposure (FERPA, COPPA implications for minors), warranting a high severity rating.

Hunters International claims to have compromised HMH and has published data (disclosed status: data_published), indicating exfiltration of company data; no ransom amount was stated and the specific data categories or volume were not detailed in the post.

high

Data the group says was taken

AI dossier — extracted from the leak post
  • Educational content and curriculum materials
  • Instructional technology platform data
  • Assessment data
  • Student and school records (potential)
  • Employee/HR records (potential)
  • Business and financial records (potential)

Original description

AI-summarised, not from the leak post

HMH, or Houghton Mifflin Harcourt, is a long-established publishing company specializing in educational content. They provide a variety of instructional technology, assessments, and other learning materials to schools in over 150 countries. The company also publishes a number of well-known trade and reference works, alongside children's books. Their goal is to foster a lifelong love of learning in every individual they serve.

Sources

Source

Indexed 9 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 Hunters International

Hunters International is a ransomware group that emerged in October 2023, operating with primarily financial motivations and demonstrating rapid expansion in their victim targeting across multiple sectors. The group's origin and specific affiliations remain largely undocumented by major security agencies, though their operational patterns suggest they function as an independent ransomware operation rather than a established Ransomware-as-a-Service model. Based on publicly available victim data, Hunters International has demonstrated a preference for targeting business services, technology, and manufacturing sectors, with their attacks primarily concentrated in English-speaking countries including the United States, France, and the United Kingdom. Their attack methodology and specific technical capabilities have not been extensively documented by major threat intelligence organizations such as CISA, FBI, or Mandiant, limiting detailed analysis of their initial access vectors, encryption methods, or data exfiltration practices. With 388 documented victims since their emergence, the group has shown consistent activity levels, though specific high-profile campaigns or notable ransom demands have not been widely reported in public threat intelligence reports. As of current reporting, Hunters International appears to remain active with no documented law enforcement disruptions or operational changes reported by major cybersecurity agencies. The group has been linked to 695 public disclosures across our corpus. First observed on a leak site on October 20, 2023; most recent post March 26, 2026. The operation is currently active.

Also tracked as: Hunters.

Timeline of this disclosure

  • October 3, 2025HMH (hmhco.com) listed by Hunters Internationalon the group's public leak site

Other recent disclosures by Hunters International

Hunters International has been linked to 695 public victims on Darkfield. A sample of the most recent:

See the full Hunters International dossier →

Sector and geography

This disclosure adds to ransomware activity in the Education sector, which has 1,082 disclosures indexed across all operators we track. Geographically, HMH (hmhco.com) is reported in United States, a country with 11,033 ransomware disclosures in our corpus.

If your organisation is affected

A listing by Hunters International means HMH (hmhco.com) 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 Hunters International'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.