Inside the LeakBase 3.6Kk ULP by blockchair: How Malware Harvested 456K Passwords
The LeakBase 3.6Kk ULP dump posted by threat actor blockchair on October 14, 2024 is a textbook example of how infostealer malware turns compromised endpoints into a credential supply chain. The 3.6 million raw records -- distilled down to 456,857 unique email-password-URL triplets -- did not come from a hacked company database. They came from individual users whose devices were infected with credential-harvesting malware. Understanding that distinction is the key to understanding why stealer logs are so persistently dangerous.
This dump is one of several released by the threat actor blockchair. Related releases include LeakBase 1.3Kk ULP by blockchair, LeakBase 1.19Kk ULP by blockchair, LeakBase 6.6GB ULP by blockchair, and How LeakBase 1.7M ULP by blockchair Leaked 198,412 Logins.
Why This Is Dangerous
ULP (URL-Login-Password) files are not theoretical threats. They are ready-to-use attack kits. The plaintext passwords in this dump bypass every cracking or brute-force step. The homepage URLs tell attackers exactly which site each credential belongs to, making targeted account takeover attempts nearly effortless. With 456,857 unique accounts exposed across a broad range of services, the potential for downstream compromise is significant.
What Was Exposed
- Email addresses -- 456,857 unique accounts
- Plaintext passwords -- no decryption needed, immediately usable
- Homepage URLs -- precise site context for each credential pair
Why This Matters
- Credential stuffing: Automated tools cycle through these email-password pairs against banking, retail, and SaaS platforms within hours of a dump going live.
- Account takeover: A compromised email account allows attackers to reset passwords on linked services, cascading one breach into many.
- Identity theft: Full login context combined with URL data allows attackers to construct targeted phishing lures or social engineering scripts.
- Fraud: Accounts linked to payment methods or loyalty programs are prioritized targets once credentials are confirmed working.
How Infostealer Malware Harvests ULP Data
Infostealer malware -- delivered via phishing attachments, trojanized software, or malvertising -- installs silently on a victim's device. Once active, it extracts saved credentials from browser storage (Chrome, Firefox, Edge), session cookies, and clipboard data. It captures the URL associated with each saved login, forming the URL-Login-Password structure seen in this dump. The harvested data is sent back to the attacker's command-and-control server, then aggregated with logs from other infections. Actors like blockchair package these aggregated logs into ULP compilations and post them on underground forums -- sometimes for profit, sometimes for reputation. Each posting dramatically multiplies how many threat actors can act on the stolen data.
Check If You Are Affected
Heroic's breach database indexes over 400 billion records from thousands of known stealer log dumps and database breaches, including this one. Search your email address now to see if your credentials appeared in the LeakBase 3.6Kk ULP release or any other known exposure -- and get clear next steps to secure your accounts.
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