Was O'Connell Mahon Architects hit by ransomware?

O'Connell Mahon Architects was listed by the Dan0N ransomware operation (Ireland), and stolen data was published on the group's leak site. Darkfield tracks this disclosure with the original leak post, screenshot and group context.

Who is the Dan0N ransomware group?

Dan0N is a ransomware operator tracked by Darkfield. See the full operator dossier for its known victims, sectors targeted, IOCs and leak-site infrastructure.

What data was leaked in the O'Connell Mahon Architects breach?

Dan0N published data attributed to O'Connell Mahon Architects (~1 TB). Darkfield captured the leak post and a screenshot of the listing.

Ransomware victim disclosure

← All victims

O'Connell Mahon Architects

Claimed by Dan0N · listed 2 years ago

1 TB

Data size

27m

Age

since listed · data leaked

Status timeline

ListedApr 25, 2024
Data leakeddate unknown

At a glance

Group: Dan0N
Status: Data leaked
Country: Ireland
Sector: Business Services
Listed on leak site: Apr 25, 2024
Data size: 1 TB

About the victim

AI dossier — public-source company profile

O'Connell Mahon Architects is an Irish architecture firm specializing in health and wellness facility design. With 60 design professionals across offices in Dublin and Cork, they have delivered over 150 healthcare projects for public and private clients over the past 30 years, ranging from small interventions to national infrastructure projects.

Industry: Architecture & Design Services (Healthcare Specialization)
Address: Offices in Dublin and Cork, Ireland
Employees: 60

Attack summary

Severity: high — Confirmed exfiltration and publication of 1 TB of data including financial, legal, employee, partner, and client information represents significant business data exposure. The scale and sensitivity of the data (particularly financial and client information for a professional services firm) elevates this to high severity.

Dan0N claims to have exfiltrated approximately 1 TB of data from O'Connell Mahon Architects, including financial records, legal documents, employee information, partner details, and client information. The group has published the stolen data.

high

Data the group says was taken

AI dossier — extracted from the leak post

Financial records
Legal documents
Employee information
Partner information
Client information

What the group claims

The total size of stolen information is 1TB. This leak contains corporate information of the company: Financial, legal, information on employees and partners. Information on clients was also received:

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 Dan0N

Dan0N is an emerging ransomware group that first appeared in April 2024, operating with primarily financial motivations and demonstrating a focused targeting approach across multiple sectors. Based on limited public information, the group's origin and affiliations remain unclear, with insufficient data to determine whether they operate as an independent entity or as part of a Ransomware-as-a-Service model. The group has demonstrated capability to compromise organizations across diverse sectors including business services, technology, healthcare, and financial services, though specific attack vectors and technical methodologies have not been extensively documented by major security research organizations. Dan0N has maintained a relatively low profile compared to established ransomware operations, with 33 documented victims primarily concentrated in the United States, Ireland, and South Korea, suggesting either targeted regional focus or opportunistic attacks against accessible infrastructure in these countries. The group appears to remain active as of current reporting, though the limited public documentation from established threat intelligence sources indicates they have not yet achieved the notoriety or scale of operations that would trigger significant law enforcement attention or comprehensive technical analysis from major security firms. The group has been linked to 33 public disclosures across our corpus. First observed on a leak site on April 25, 2024; most recent post August 23, 2024. The operation is currently inactive.

Timeline of this disclosure

April 25, 2024O'Connell Mahon Architects listed by Dan0Non the group's public leak site

Data size: 1 TB

Other recent disclosures by Dan0N

Dan0N has been linked to 33 public victims on Darkfield. A sample of the most recent:

See the full Dan0N 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, O'Connell Mahon Architects is reported in Ireland, a country with 43 ransomware disclosures in our corpus.

If your organisation is affected

A listing by Dan0N means O'Connell Mahon Architects 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, NCSC-IE (Ireland), as required for your jurisdiction.
Monitor for the data appearing on Dan0N'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.