This record tracks a ransomware attack claimed by the
thegentlemen group against
Tentac. 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.
0days open
t1 · Published
t2 · Pending
Published
September 14, 2026
Disclosed / Notified
Not disclosed yet
Attack Summary
tentac.co.jp is an entity identified within the threat-intelligence index under the listing type ransomware victim. Operating within the IT sector and located in Japan, the entity represents a target profile relevant to cybersecurity monitoring and incident analysis. The association with thegentlemen frames its inclusion in the index as a documented ransomware incident linkage. This description maintains factual neutrality regarding operational details, avoiding speculation about breach specifics, data exposure, or recovery outcomes. The listing serves as a reference point for threat actors, defenders, and analysts tracking ransomware activity across the Japanese IT landscape.
Leak Screenshots
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Dark Web Exposure
Findings for tentac.co.jp
— indexed by HaveIBeenRansom.
0
found in Infostealer logs
91
found in Traditional breaches
12
found in Ransomware leaks
Dropbox_BF.7z
B F R e p o V 3 F i l e s · breach
••• emails
Full Clouds Cit0day_2.7z.001
DBs w MTDT · breach
••• emails
Cit0day [cit0day.in] breaches.csv
LKnet reserve chat · breach
••• emails
OnlinerSpambot_BF.7z
B F R e p o V 3 F i l e s · breach
••• emails
Access Intelligence
play · ransomware
••• emails
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