Inside X507 Hotmail Stealer Logs: 506 Passwords Harvested

HEROIC analyzed a stealer log file labeled X507 Hotmail, uploaded to Telegram in March 2025, containing 506 compromised Hotmail credential records. The data was harvested through infostealer malware that extracted credentials from browser password stores and active login sessions on infected endpoints, then compiled into a structured format specifically targeting Hotmail and Microsoft account holders.

Plaintext Passwords Bypass All Cryptographic Protections

The 506 passwords in this collection are stored in raw plaintext. From a technical standpoint, this is the worst-case scenario for credential security. There are no bcrypt hashes to crack, no salting to complicate rainbow table attacks, and no key derivation functions to slow down exploitation. Each credential is a direct, plaintext string that maps to a working Hotmail login.

What Was Exposed

• Email Addresses — Hotmail accounts that function as Microsoft account identifiers across Outlook, OneDrive, and other services
• Plaintext Passwords — raw credential strings extracted from browser databases and keystroke captures
• URLs — the authentication endpoints and login portals where these credentials were intercepted

Credential Reuse Makes 506 Records Far More Impactful

Although 506 records is a modest number, credential stuffing transforms each entry into a multi-target attack vector. Automated tools take each Hotmail credential and test it against popular services — banks, streaming platforms, social networks, and cloud providers. Since Hotmail serves as a Microsoft account, a compromised password may also unlock OneDrive, Skype, Xbox, and any enterprise Microsoft 365 environments linked to the same credentials.

Technical Profile of the Infostealer Attack Chain

The X507 Hotmail data was generated through a standard infostealer attack chain. The malware infiltrates a device via a dropper — typically embedded in a trojanized installer or delivered through a phishing campaign. Upon execution, it targets Chromium-based and Firefox browser credential databases, decrypting locally stored passwords using the operating system's credential protection APIs. It simultaneously deploys a keylogger to capture credentials entered manually and a cookie stealer to hijack authenticated sessions. The harvested data is exfiltrated via HTTPS to a collection server, formatted into logs, and distributed through Telegram.

Check If Your Credentials Were Exposed

The X507 Hotmail collection has been indexed in the HEROIC data breach scanner. With over 400 billion records in its database, HEROIC can determine in seconds whether your email or password appears in this or any other known data breach. Search your Hotmail credentials now, replace any that appear compromised, and enable two-factor authentication to add a security layer that survives even a password leak.