How Stealer Malware Works: LeakBase 11M ULP by cuarzoAlfo Exposes 526,268 Credentials

HEROIC analysts found that 526,268 unique records were exposed in the LeakBase 11M ULP stealer log released by threat actor cuarzoAlfo on June 30, 2024. The dataset, distributed on underground forums, contains email addresses, plaintext passwords, and homepage URLs harvested by information-stealing malware from infected devices. This release is part of a broader pattern of ULP (URL:Login:Password) credential dumps regularly published on LeakBase, a well-known hacking forum used for distributing stolen credential collections. Related releases in this series include LeakBase ULP #Free, LeakBase ULP #Free1, and LeakBase ULP by vaxima.

Why This Is Dangerous

Stealer logs contain credentials captured directly from victims' devices by malware, meaning the passwords are recorded exactly as the user typed them, in plaintext. This bypasses all server-side protections such as hashing or salting. Every email-password pair in this dataset represents a working credential at the moment it was stolen. Attackers can immediately load these pairs into automated tools and test them against hundreds of other websites and services where victims may have reused the same password.

What Was Exposed

• Email Address
• Plaintext Password
• HomePage URL

Why This Matters

The inclusion of homepage URLs alongside credentials reveals which specific websites victims were logged into when the malware executed. This allows attackers to target high-value accounts with precision, focusing first on financial services, webmail, and corporate portals identified in the URL field. Credential stuffing attacks using stealer log data contribute directly to account takeover fraud, unauthorized financial transactions, identity theft, and the resale of compromised accounts on dark web marketplaces.

How Stealer Log Breaches Work

Stealer logs are produced by information-stealing malware, sometimes called infostealers, that infects individual computers and mobile devices. Once installed, the malware silently captures credentials saved in browsers, typed into login forms, or stored in password managers. It also records the URLs of sites the victim visited while infected. The harvested data is transmitted to an attacker-controlled server, compiled into structured logs, and then sold or freely distributed on underground forums. Unlike traditional database breaches, stealer logs target the endpoint rather than the server, making them difficult to detect and prevent through standard corporate perimeter defenses.

Check If You Are Affected

HEROIC offers a free identity scanner that checks your email address against more than 400 billion exposed records, including stealer log data of this type. Visit heroic.com to run a free scan and find out whether your credentials appear in known data dumps. If your email appears in this dataset, change your passwords on all associated accounts immediately, prioritizing any services identified by the homepage URLs in the log, and enable two-factor authentication wherever it is available.

Related Parts of This Breach

• LeakBase ULP #Free - 95,333 Records
• LeakBase ULP #Free1 - 95,231 Records
• LeakBase ULP by vaxima
• LeakBase ULP Kall - 62,386 Records