Japanese Users Targeted: nifty.ne.jp Stealer Log Exposes 1,135 Passwords

HEROIC analysts have identified a stealer log file posted to Telegram on June 23, 2026, containing 1,135 compromised records linked to nifty.ne.jp — a major Japanese internet service provider. The exposed data includes email addresses, plaintext passwords, and URLs captured from infected devices. This breach puts Nifty email users at immediate risk of unauthorized account access.

Why Plaintext Passwords Eliminate Every Line of Defense

The credentials in this stealer log are stored as plaintext, meaning they are completely readable without any decryption or cracking. An attacker who accesses this Telegram dump can log into affected nifty.ne.jp accounts within seconds, bypassing what should be the most fundamental layer of account security.

For Japanese internet users relying on Nifty for email and web services, the exposure of plaintext passwords creates an urgent window of vulnerability. Every hour these credentials remain unchanged is another hour attackers can use them to access email inboxes, intercept communications, and pivot to connected accounts.

What Was Exposed in the nifty.ne.jp Dump

• Email Addresses — nifty.ne.jp email accounts that function as primary identifiers for internet services, financial platforms, and personal communications in Japan.
• Plaintext Passwords — Fully readable passwords that require no technical expertise to exploit, enabling immediate unauthorized access to victim accounts.
• URLs — Web addresses visited by the compromised users, providing attackers with a clear map of which online services and platforms to target.

Why This Breach Extends Beyond nifty.ne.jp Alone

Japanese internet users commonly tie their ISP email address to a wide range of services, from online banking and government portals to e-commerce and subscription services. A compromised nifty.ne.jp password does not just threaten the email account — it potentially unlocks every service where that same email and password combination was used.

Credential-stuffing attacks leverage exactly this behavior. Automated tools take the 1,135 stolen email-password pairs and test them against thousands of websites in rapid succession. Given that password reuse rates typically exceed 60%, a significant portion of these credentials will work on at least one additional platform, expanding the breach footprint dramatically.

How Stealer Logs Compromise Devices Across Borders

Infostealer malware does not respect geographic boundaries. It spreads through phishing campaigns, malicious software bundles, and compromised websites, infecting devices regardless of the user's location. Once installed, it systematically harvests browser-stored credentials, session cookies, and auto-fill data from the victim's machine.

The stolen credentials are packaged into log files and funneled through command-and-control infrastructure before being distributed via Telegram channels and underground marketplaces. The nifty.ne.jp data in this dump was collected from endpoints infected by this type of malware, then compiled and shared publicly on Telegram where it remains accessible to a global audience of threat actors.

Check If Your Credentials Were Exposed

If you use a nifty.ne.jp email address, verifying your exposure is essential. HEROIC's free breach scanner lets you search across more than 400 billion compromised records to determine whether your email or password appears in this or any other known data breach. If you find your credentials in the results, change your nifty.ne.jp password immediately, enable any available multi-factor authentication, and update passwords on every service where you used the same login combination.