The Password Reuse Crisis Hits a New High: 183 Million Credentials Dumped from Malware Stealer Logs
Password reuse just became a lot more dangerous. In what may be one of the largest credential-harvesting operations ever documented, threat actors have compiled 3.5 terabytes of stolen login data—now labeled the “Synthient Stealer Log Threat Data”—and it’s been added to Have I Been Pwned (HIBP). The dataset includes 183 million unique email addresses, each paired with the passwords and websites where they were stolen. For the average person juggling dozens of logins across apps and services, that’s an alarming development. “The risk isn’t just about a single password getting exposed anymore,” says Sachin Jade, Chief Product Officer at Cyware. “Credential-based attacks have become a leading cause of breaches, so organizations need real-time visibility into compromised credentials and how they connect to broader attack vectors.”
The Anatomy of the Synthient Data Dump
The Synthient dataset originated from malware known as infostealers—programs designed to silently pluck passwords and cookies from infected devices before exfiltrating them to criminal marketplaces. Synthient, a threat-intelligence company, aggregated billions of these stolen records, then cleaned and normalized the data before sharing it for research.
After verification, HIBP found 183 million unique email addresses, and 91 percent of them had already appeared in previous breaches. That means nearly 17 million email-password combinations are newly exposed—and millions more confirm the sheer persistence of password reuse.
The breach occurred in April 2025, but wasn’t added to HIBP until October, showing how long stolen data can circulate in underground forums before entering the public eye. “By the time we see a dataset like this, the criminals have already had months to exploit it,” Jade notes. “That’s why continuous credential monitoring is so important—it closes the visibility gap.”
Why This Matters
This isn’t just another dump of leaked passwords. Because each record links a password to a specific website, attackers can launch immediate credential-stuffing attacks—testing the same login across banks, retailers, and streaming services. And with automation, they can do it at massive scale.
According to Jade, that’s exactly why organizations are shifting toward identity-centric defense models. “Credential monitoring and management have become essential parts of a mature cybersecurity strategy,” he explains. “By correlating compromised credentials with network and endpoint threat indicators, security teams can detect misuse faster and coordinate response across layers of defense—network, application, and identity.”
In other words: credentials aren’t just another threat surface—they’re the connective tissue between every system attackers touch.
What to Do If You’re Affected
If your email shows up in HIBP’s Synthient database, assume the password tied to it has been compromised—and probably used elsewhere. Change it immediately, along with any account that shares that password. Then enable two-factor authentication (2FA) everywhere you can.
A reputable password manager can also generate and store unique passwords for every site, insulating you from future leaks.
Organizations, meanwhile, need to think bigger than one-off resets. Integrating credential-exposure data into incident response, identity and access management (IAM), and threat intelligence pipelines is now table stakes. Jade says the most forward-thinking teams are going even further: “Aligning credential monitoring with the company’s overall risk management framework helps prioritize response based on contextual risk rather than isolated incidents,” he says. “That turns credential management from a reactive safeguard into a proactive risk-governance mechanism.”
The Bigger Picture
The Synthient leak reinforces a harsh reality: our digital identities are already under constant attack. Have I Been Pwned now tracks over 15 billion compromised accounts across more than 900 documented breaches. For most people, the question isn’t if their data is in one of them—it’s how many times.
Password reuse, convenience, and delay all play directly into attackers’ hands. Each time you reuse a login, you extend the lifespan of your own vulnerability.
As Jade puts it, identity is now the true perimeter. Firewalls, antivirus, and network defenses matter—but none of them help if your password is already sitting in a criminal marketplace. “The more organizations treat credentials as dynamic risk indicators rather than static secrets,” he says, “the more resilient they’ll be when—not if—this happens again.”