This record tracks a ransomware attack claimed by the
rhysida group against
Cheyenne & Arapaho Tribes. It collects the publicly disclosed attack details — sector, location and
timeline — as published on the operator's leak site and indexed by Breach House.
Window Zero
EXPOSURE GAP
Window Zero is the time the breach stayed in the open before
anyone said so — the gap between when the attack was first discovered
on the operator's leak site (t1) and when it was publicly disclosed (t2).
The wider this window, the longer victims, staff and customers were exposed with no warning.
-70days
t1 · Published
t2 · Disclosed
Business Category
Public Sector
Published
February 17, 2026
Disclosed / Notified
Dec 10, 2025
Attack Summary
Cheyenne & Arapaho Tribes The Cheyenne and Arapaho Tribes are a federally recognized united nation of two distinct peoples-the Tsistsistas (Cheyenne) and Hinono'ei (Arapaho)-with a historic alliance formed in the early 19th century.
Leak Screenshots
SAMPLE
Proof-of-breach screenshots the operator posted from the stolen data. Previews are
redacted and locked — the originals are available on HaveIBeenRansom.
Dark Web Exposure
Findings for cheyenneandarapaho-nsn.gov
— indexed by HaveIBeenRansom.
0
found in Infostealer logs
5
found in Traditional breaches
95
found in Ransomware leaks
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••• emails
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play · ransomware
••• emails
UnderArmour_BF_.7z.001
Database World ROC · breach
••• emails
pureincubation-com.7z.001
Database World ROC · breach
••• emails
San Pasqual Band of Mission Indians
medusa · ransomware
••• emails
Arandell Corp
medusa · ransomware
••• emails
McGraw Hill, Inc. (mheducation.com)
shinyhunters · breach
••• emails
PENS.COM
clop · ransomware
••• emails
Leak volumes are locked
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Legal Disclaimer:
This ransomware victim record reflects information published on the operator's leak site.
Breach.house does not acquire, download, host, access or redistribute unlawfully obtained data. It indexes only publicly visible information posted by ransomware, breach and infostealer operators and open web sources, without accessing the underlying stolen content. The service supports public awareness, legitimate research and cyber-resilience.