How Infostealer Malware Led to 1,664 Stolen Logins in the 39 Boss Telegram Upload

In June 2023, HEROIC's threat intelligence team identified a stealer log file uploaded to Telegram by a user operating as 39 Boss. The dataset contained 1,664 records with email addresses, plaintext passwords, and the URLs of services where the credentials were harvested. Understanding how this type of breach happens is critical for anyone who wants to protect themselves from similar attacks in the future.

Why This Is Dangerous

Infostealer malware, the tool that generated the 39 Boss log, is one of the most effective credential theft mechanisms available to cybercriminals. It operates silently and leaves no obvious trace. The 1,664 records in this upload contain everything an attacker needs: a target email address, the exact plaintext password, and the URL of the service where the password was used. There is no barrier between this data and a succesfull account takeover.

What Was Exposed

The 39 Boss Telegram stealer log contained the following data types for each of the 1,664 compromised records:

• Email Addresses
• Plaintext Passwords
• URLs (endpoint and API host addresses)

Why This Matters

The 39 Boss stealer log feeds directly into credential stuffing pipelines. Cybercriminals use automated tools to test each of the 1,664 email and password pairs against popular banking sites, email providers, and corporate platforms. Since most people reuse passwords accross multiple services, even a single compromised credential can unlock several accounts at once. The results include identity theft, unauthorized financial transactions, account lockouts, and in business contexts, full network intrusion.

How Infostealer Malware Led to 1,664 Stolen Logins

The 39 Boss upload began with infostealer malware landing on victims' devices, most likely through phishing emails disguised as shipping notifications, invoice requests, or software updates. Once installed, the malware scanned each infected device for browser-saved passwords, logging the credential and its associated URL for every saved login it found. All harvested data was compiled into a structured log file and transmitted to a command-and-control server. The operator, 39 Boss, then packaged this log and uploaded it to Telegram where criminal buyers could download and use the credentials. The entire process from infection to upload typicaly takes less than 24 hours.

Check If You Are Affected

If your email address was captured by the 39 Boss stealer log, your credentials may already be circulating in criminal markets. HEROIC's free breach scanner searches more than 400 billion exposed records to show you exactly what has been compromised. Search your email today and take action before your accounts are targeted.