Disclosure context

About Rhysida

Rhysida is a ransomware group that emerged in June 2023, operating with primarily financial motivations through targeted attacks against critical infrastructure and public sector organizations. The group's origin and potential state affiliations remain unclear, though they operate independently rather than as a traditional Ransomware-as-a-Service model, with limited public documentation regarding connections to other cybercriminal organizations. Rhysida employs double extortion tactics, typically gaining initial access through compromised VPN credentials and exploiting vulnerable public-facing applications before deploying their ransomware payload and exfiltrating sensitive data prior to encryption. The group has demonstrated a particular focus on healthcare and educational institutions, with notable attacks documented by CISA and FBI advisories highlighting their targeting of hospitals and school districts across multiple countries, resulting in significant operational disruptions to critical services. As of late 2024, Rhysida remains an active threat with continued operations targeting organizations primarily in the United States, Canada, and other Western nations, maintaining their focus on high-value sectors where operational disruption can maximize ransom payment likelihood. The group has been linked to 278 public disclosures across our corpus. First observed on a leak site on June 5, 2023; most recent post May 20, 2026. The operation is currently active.

Timeline of this disclosure

January 25, 2026Cytek Biosciences listed by Rhysidaon the group's public leak site

Data size: 10 TB
Records: 287 files

Sector and geography

This disclosure adds to ransomware activity in the Healthcare sector, which has 1,779 disclosures indexed across all operators we track. Geographically, Cytek Biosciences is reported in United States, a country with 7,392 ransomware disclosures in our corpus.

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.

Ransomware victim disclosure

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Cytek Biosciences

Claimed by Rhysida · listed 4 months ago

10 TB

Data size

287 files records

Age

since listed · data leaked

Status timeline

Listed
Jan 25, 2026
Data leaked

At a glance

Group: Rhysida
Status: Data leaked
Country: United States
Sector: Healthcare
Listed on leak site: Jan 25, 2026
Data size: 10 TB
Records: 287 files

About the victim

AI dossier — public-source company profile

Cytek Biosciences is a leading cell analysis solutions company founded in 1992 and headquartered in Fremont, California. The company develops and manufactures instruments and reagents for flow cytometry and cell analysis, serving research and clinical markets. It maintains global offices across North America, Europe, and Asia.

Industry: Cell Analysis & Life Sciences Instrumentation
Address: Fremont, California, United States
Founded: 1992

Attack summary

Severity: high — Rhysida claims confirmed exfiltration and sale of Cytek Biosciences data to a third party. As a life sciences / biotech instrumentation company, the data likely includes proprietary R&D, intellectual property, and potentially employee/customer PII. Sale to an undisclosed buyer amplifies risk of further misuse.

Rhysida claims to have exfiltrated data from Cytek Biosciences and states that all data was sold to a buyer; no specific data catalog size or file count is listed for this victim, and the data is not stated to have been publicly released.

high

Data the group says was taken

AI dossier — extracted from the leak post

Sold exfiltrated company data (contents unspecified)

What the group claims

Cytek Biosciences Cytek Biosciences is a leading cell analysis solutions company founded in 1992 and headquartered in Fremont, California with global offices across North America, Europe, and Asia. Sold 0% All data was sold, stay with us, we will upload new Companies later More

The leak post

captured from the group's site

STELIA North America is an aerospace and defence company specializing in the design, development, and manufacturing of composites.10 TB of confidential data!Data from major partner companies, such as: Lockheed Martin, Northrop Grumman, Sikorsky, Leonardo, L3Harris, Airbus Atlantic, Boeing, Bombardier, De Havilland, ARDE, MDA.
Data Catalog: 9,3 Tb, 4 324 287 Files 
All files was uploaded to public access, data hunters, enjoy 
[Southold Town Senior ServicesSouthold Police Department](https://www.southoldtownny.gov)
The Town of Southold, New York provides various government services including forms and permits, online payments, and notifications for residents. Southold Police Department is a company that operates in the Local industry.
Data Catalog: 1,7 Tb, 767 693 Files 
All files was uploaded to public access, data hunters, enjoy 
Rohner designs and builds high-quality, custom paint booths and manufactured industrial paint systems. Our quality and service, cutting-edge technology, and engineering experience provide the best value in the finishing equipment industry.
Data Catalog: 3 Tb, 3 924 397 Files 
All files was uploaded to public access, data hunters, enjoy 
The Cheyenne and Ar…

Sources

Leak posthttp://rhysidafohrhyy2aszi7bm32tnjat5xri65fopcxkdfxhi4tidsg7cad.onion/archive.php/archive.php?company=240

Source

Indexed 4 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.