Leaked Credentials Detection: How to Find Exposed Employee Passwords

Learn how to detect leaked employee credentials before attackers use them to breach your network.

Your employees’ credentials are probably already circulating on the dark web. That’s not paranoia. SpyCloud’s 2025 Identity Threat Report identified 850 billion exposed identity assets. According to IBM X-Force, infostealer malware infections increased 84% in 2024 (IBM X-Force 2025).

The fastest-growing source of leaked corporate credentials isn’t data breaches. It’s infostealer malware. When an employee’s device gets infected, every credential they type or have saved gets harvested and sold on criminal marketplaces within days.

Stolen credentials were the second most common initial access vector in 2024 (M-Trends 2025). When attackers already have valid passwords, they don’t need to hack anything. They just log in.

This guide breaks down credential detection for security teams: where to look, how to operationalize it, and what to do when credentials surface.

Where Do Leaked Corporate Credentials Appear?

Corporate credentials leak through multiple channels. Security teams need visibility into all of them to catch exposures before attackers exploit them.

Infostealer logs: Infostealers like LummaC2, RedLine, and Raccoon capture credentials as employees type them and steal passwords saved in browsers. When an employee’s device gets infected, every credential they enter or have saved gets exfiltrated. That includes their corporate VPN, Okta SSO, AWS console, and every other work application they accessed from that device. These logs appear on marketplaces within days, sometimes hours.

Dark web marketplaces: Criminal marketplaces like Russian Market, 2easy, and Genesis Market specialize in selling access credentials. Attackers can search by corporate domain and find every credential harvested from your employees’ infected devices.

Third-party breaches: When services your employees use get breached, those credentials leak too. If employees reuse passwords, a breach at a personal service can expose corporate access.

Private forums and Telegram channels: Initial access brokers trade corporate credentials on access-restricted forums. Telegram channels appear and disappear rapidly, trading fresh credentials and announcing new breach data. These sources aren’t indexed by search engines and are often not publicly accessible.

Ransomware leak sites: When ransomware groups exfiltrate data before encryption, stolen credentials often appear on leak sites. Early detection gives security teams time to force password resets before wider exploitation.

The challenge isn’t just finding leaked credentials. It’s finding them fast enough to act before attackers do. The IBM X-Force 2025 Threat Intelligence Index found that credential harvesting occurred in 29% to 46% of incidents across industries in 2024.

How to Implement Leaked Credentials Detection

Deploying enterprise credential detection involves more than subscribing to a threat feed. Security teams need to integrate detection into their existing workflows.

Define your monitoring scope:

Start with your corporate domains and critical subdomains. Add executive names and high-value targets (finance, IT admins, developers with production access). Include third-party services where employees use corporate credentials.

Establish alert workflows:

When leaked credentials surface, you need a response playbook. Who gets notified? What’s the SLA for forced password resets? How do you investigate whether the credential was already exploited? Build these workflows before you need them.

Integrate with your security stack:

Credential alerts should flow into your SIEM or SOAR platform. If you detect a leaked VPN credential, your SOC should immediately check authentication logs for that user. Integration enables faster response.

Track metrics that matter:

Measure time from detection to password reset. Track how many credentials surface per month and from which sources (breach vs. infostealer vs. phishing). Monitor recidivism to identify employees whose credentials leak repeatedly.

Consider the infostealer angle:

When credentials leak from infostealers rather than breaches, the employee’s device is likely compromised. A password reset isn’t enough. You need to launch an endpoint investigation to determine the infection scope and potential lateral movements made.

Prioritize based on access level:

Not all leaked credentials carry equal risk. A marketing coordinator’s credentials matter less than a domain admin’s. Prioritize alerts based on the access level associated with the compromised account. VPN credentials, cloud admin accounts, and privileged access should trigger immediate response. Standard user accounts can follow normal remediation workflows.

Risk-Based Credential Triage Framework

Alert fatigue kills credential monitoring programs. When every leaked credential triggers the same response, security teams either burn out or start ignoring alerts. The goal is to respond to critical leaks fast and handle lower-risk exposures through your normal process.

Risk factors to evaluate:

Response tiers:

Critical (respond in < 1 hour): Domain admin credentials, VPN access with session tokens, cloud infrastructure accounts, any credential with MFA bypass tokens. Disable immediately, terminate all sessions, initiate a full investigation.

High (respond in < 4 hours): Developer accounts with code repository access, finance systems, HR systems with PII access. Force a password reset, review recent activity, verify MFA enrollment.

Medium (respond in < 24 hours): Standard employee accounts, SaaS application access, email-only credentials from old breaches. Queue for a password reset, send a notification, log for metrics.

Low (batch processing): Former employee accounts (verify disabled), credentials from breaches over 2 years old with no session data, accounts already using hardware MFA. Document and include in weekly security report.

Integrating Detection with SIEM and SOAR

Credential alerts shouldn’t live in a separate dashboard your team checks occasionally. They need to flow into your existing security operations workflow.

SIEM integration:

Configure your credential monitoring platform to push alerts directly to your SIEM. Each alert should include enrichment data: the affected username, leak source, timestamp, whether session tokens were included, and the credential’s access level if your IAM system provides it. This lets analysts correlate credential exposures with authentication logs in a single view.

Build detection rules that fire when a leaked credential matches recent authentication activity. If a credential surfaces on a dark web marketplace and that same account authenticated from an unusual location in the past 72 hours, escalate immediately. The credential may already be in use.

SOAR playbook automation:

Automate the routine response steps so analysts focus on investigation rather than ticket creation. A basic leaked credential playbook should:

1. Create an incident ticket with all alert metadata
2. Query your IAM system for the account’s access level and group memberships
3. Check authentication logs for the past 7 days
4. If high-risk: automatically disable the account and page the on-call analyst
5. If medium-risk: send a password reset notification and create a follow-up task
6. Update the ticket with all of the gathered context for an analyst to review

IAM integration:

Connect your credential monitoring to your identity provider. When critical credentials leak, trigger automated account lockout through your IAM system. For less critical exposures, automatically enroll the user in a forced password reset flow on their next login. This removes manual steps that slow response time.

Track which users appear repeatedly in credential leaks. Some employees are credential leak magnets, often due to password reuse or poor security hygiene. Flag repeat offenders for targeted security training or additional access restrictions.

What Should Security Teams Do When Credentials Leak?

Detection without response is just expensive awareness. When your detection catches leaked credentials, speed matters.

Immediate actions:

1. Force a password reset for the affected account. Don’t send a friendly reminder. Disable the old password immediately and require a reset on the next login.
2. Check authentication logs. Look for signs the credential was already used. Unusual login times, unfamiliar locations, or impossible travel patterns indicate an active compromise.
3. Review the leak source. Third-party breach credentials may be months old with limited exposure. Infostealer-sourced credentials tend to be fresher and higher risk. The employee’s device needs investigation as well.
4. Assess the blast radius. If the credential provides access to sensitive systems (VPN, cloud admin, production databases), assume those systems may be compromised and investigate accordingly.
5. Update detection rules. If the credential appeared with session cookies or MFA bypass tokens, attackers may have persistent access even after a password reset. Check for active sessions.

For infostealer-sourced credentials:

When credentials come from infostealers, you have a bigger problem than a leaked password. The employee’s device is infected, and everything accessed from that device may be compromised. Initiate an endpoint investigation, check for lateral movement, and consider what else the infostealer captured (session cookies, autofill data, screenshots, documents).

Watch for stolen session tokens:

Modern infostealers don’t just capture passwords. They also exfiltrate session cookies and authentication tokens that let attackers bypass MFA entirely. Say an employee was logged into Okta when the infostealer ran. Attackers now have session tokens that work even after you’ve reset the password.

Check for and terminate all active sessions for compromised accounts. Review recent activity for signs of session hijacking. Attackers use stolen cookies within minutes of buying them. They access accounts without triggering any login prompt. That’s why your detection needs to catch session tokens, not just passwords.

For detailed breach response procedures, see our guide on what to do when passwords are exposed in a breach.

How to Reduce Credential Exposure Risk

Detection catches credentials after they leak. Prevention reduces how many leak in the first place.

Enforce MFA everywhere. Two-factor authentication doesn’t prevent credential theft, but it limits what attackers can do with stolen passwords. Even leaked credentials become less useful without the second factor. Prioritize MFA on VPN, SSO, cloud consoles, and any system with sensitive access. CISA’s guidance on phishing-resistant MFA recommends FIDO2 or PKI-based authentication for high-value targets.

Deploy endpoint protection that catches infostealers. EDR solutions should detect common infostealer families. But infostealers evolve rapidly, so don’t assume your current tooling catches everything. Make sure your EDR is configured to detect credential theft behavior, not just known malware signatures.

Limit credential sprawl. Every application where employees create accounts with corporate email is another breach waiting to happen. Consolidate authentication through SSO where possible. Fewer credentials means a smaller attack surface. NIST’s Digital Identity Guidelines provide detailed recommendations for enterprise authentication architecture.

Train employees on phishing. Phishing attacks bypass technical controls by harvesting credentials directly from users. Regular training and simulated phishing campaigns reduce success rates.

Monitor for password reuse. Employees reusing corporate passwords on personal accounts create risk you can’t control. Some credential detection platforms can identify when corporate passwords appear in non-corporate breach data, indicating reuse.

How Fast Do Attackers Exploit Leaked Credentials?

Speed matters in credential detection because attackers don’t wait. The timeline from credential theft to exploitation has compressed dramatically.

Infostealer credentials: Within 24-72 hours of infection, stolen credentials appear on marketplaces like Russian Market. Attackers who purchase these logs often attempt access within hours of acquisition. For high-value corporate targets, the window may be even shorter.

Third-party breach credentials: These vary more widely. Major breaches may circulate privately for weeks or months before public disclosure. By the time breaches become public knowledge, attackers have already sifted through the data for valuable corporate access.

Initial access broker sales: Credentials sold through initial access brokers (IABs) on criminal forums often include verified access. These fetch premium prices precisely because the seller has confirmed the credentials work. Buyers expect immediate utility.

The practical implication: detection that takes weeks or months provides minimal value. By the time you discover leaked credentials through annual audits or quarterly reviews, attackers have already exploited them. Continuous monitoring with real-time alerting is the only approach that gives security teams a fighting chance.

Conclusion

Leaked credentials detection isn’t optional for enterprise security. In 30% of incidents, attackers aren’t breaking in—they’re logging in with valid credentials (IBM X-Force 2025). Detection that only covers old breaches misses today’s primary threat: infostealers.

To avoid credential-based breaches, you need continuous detection across dark web markets, infostealer logs, and private forums. You also need alert workflows that force password resets within hours of detection, not days or weeks.

Attackers move fast. Your detection needs to move faster.

For enterprise-grade leaked credentials detection that covers infostealer marketplaces and dark web combo lists, learn how compromised credential monitoring protects your organization’s credentials before they’re exploited.