How to Check If Employee Credentials Are Compromised

Learn how to detect compromised employee credentials before attackers exploit them to breach your network.

Your employees’ credentials are probably already circulating somewhere you can’t see. That’s not paranoia. It’s math. According to IBM’s X-Force 2025 Threat Intelligence Index, valid account credentials tied with exploits at 30% of all initial access vectors. Attackers aren’t breaking in. They’re logging in.

The problem? Most organizations don’t check. They assume password policies and MFA will handle it. Then they discover an attacker has been inside their network for weeks using credentials they didn’t know were leaked.

Mandiant’s M-Trends 2025 report found that stolen credentials accounted for 16% of intrusions in 2024, up from 10% in 2023. That’s a 60% increase in one year. The trend is clear: credential theft is accelerating, and organizations that don’t actively check for compromised credentials are flying blind.

This guide walks through practical methods to check if employee credentials are compromised and what to do when you find them.

Why Should Security Teams Check Employee Credentials?

Most security teams focus on blocking attacks. But what happens when attackers already have valid credentials? They don’t need to hack anything. They just log in.

The numbers tell the story. IBM’s X-Force 2025 Threat Intelligence Index found that 84% more infostealer malware was delivered via phishing compared to the previous year. SpyCloud’s Identity Threat Report 2025 revealed that only 20% of organizations consistently revoke or reset credentials after phishing attacks. That means 80% of organizations are leaving compromised credentials active in their environment.

Here’s what makes credential exposure particularly dangerous: attackers blend in. When someone logs in with valid credentials, they look like a legitimate user. No alerts fire. No anomalies trigger. Your security tools see normal authentication.

The window between credential theft and exploitation keeps shrinking. Infostealer credentials appear on marketplaces within days of infection. Third-party breaches circulate on private forums before public disclosure. If you’re not actively checking for compromised credentials, you’re waiting for attackers to find them first.

SpyCloud’s research found that 35% of security professionals rated exposed or weak credentials as the riskiest entry point to their organization. They’re right to worry. When attackers can simply log in with valid credentials, your perimeter defenses become irrelevant.

Checking for compromised credentials isn’t just good practice. It’s the difference between catching a threat actor at the door and finding them already inside your network.

Where Do Compromised Employee Credentials Appear?

Corporate credentials leak through multiple channels. You need visibility into all of them to catch exposures before attackers do.

Infostealer logs and marketplaces: When an employee’s device gets infected with malware like RedLine or Raccoon, every credential they enter gets harvested. Vidar and LummaC2 do the same thing. Corporate VPN logins, SSO portals, cloud consoles, everything. These logs hit specialized marketplaces within days. Sometimes hours.

The IBM X-Force 2025 report documented a 12% year-over-year increase in infostealer credentials for sale on the dark web. These aren’t old breach records. They’re fresh credentials from recently infected machines, often including active session tokens that bypass MFA entirely.

Third-party breach databases: When services your employees use get breached, those credentials leak too. If employees reuse passwords (SpyCloud found 41% credential reuse), a breach at a personal service can expose corporate access. Third-party breaches often circulate privately for weeks or months before public disclosure. See our guide on leaked credentials detection for a deeper dive on finding exposed passwords.

Dark web forums and Telegram channels: Initial access brokers sell corporate credentials on access-restricted forums. Telegram channels appear and disappear rapidly, leaking fresh credentials and announcing new breach data. These sources aren’t indexed by search engines and require specialized monitoring to access.

Combo lists and credential dumps: Attackers compile credentials from multiple breaches into massive combo lists used for credential stuffing attacks. Old breach data stays dangerous as long as employees reuse passwords. Attackers know this. These lists get traded across forums and fed into automated attack tools.

Ransomware leak sites: When ransomware groups exfiltrate data before encrypting their victim’s network, stolen credentials often appear on leak sites. Early detection gives you time to force password resets before wider exploitation. Ransomware gangs like LockBit and ALPHV routinely publish stolen data including authentication credentials. Cl0p does the same.

The challenge isn’t finding one source to monitor. It’s maintaining visibility across all of them continuously.

How Can You Check If Corporate Credentials Are Exposed?

Checking for compromised credentials requires multiple approaches. No single method catches everything.

Method 1: Active Directory Password Auditing

Start with what you control. Active Directory password auditing scans your environment against known breach databases to identify passwords that have already been exposed.

Tools like Specops Password Auditor (free) and Azure AD Password Protection compare hashed passwords against breach databases. When they find a match, they flag accounts using compromised passwords for immediate reset.

When to use this method:

• Quarterly audits as a baseline
• After major breach announcements affecting popular services
• As part of new employee onboarding verification
• During compliance audits requiring password hygiene documentation

How to implement: Run the audit against your entire Active Directory. Export results showing which accounts use breached passwords. Prioritize privileged accounts for immediate reset. Create a remediation plan for the rest based on risk level.

Limitations: This only catches passwords that match known breach data. It won’t detect credentials stolen by infostealers or exposed in private breaches. Cloud services that don’t sync with AD? Those get missed too.

Method 2: Dark Web Monitoring

Dark web monitoring gives you continuous visibility into criminal marketplaces and forums where stolen credentials appear.

Enterprise monitoring differs from point-in-time scans. It tracks your corporate domains across dark web markets and infostealer channels. Private forums too. When credentials surface, you get alerted immediately.

What enterprise monitoring covers that free tools don’t:

• Private forums requiring invitation or reputation to access
• Infostealer marketplace logs sold by infection, not by breach
• Telegram channels that appear and disappear rapidly
• Fresh breach data before it becomes widely distributed
• Session tokens and API keys that bypass authentication

The value is speed. Find out about compromised credentials in hours, not weeks. That’s the difference between a password reset and an incident investigation.

Setting up effective monitoring: Start by listing all your corporate domains. Include subsidiaries and acquired companies. Add executive names for targeted monitoring. Don’t forget third-party services where employees use corporate email. Configure alerts to flow into your existing workflow.

Method 3: Threat Intelligence Integration

Credential alerts become more valuable when they flow into your existing security operations.

Configure your credential monitoring platform to push alerts directly to your SIEM. Each alert should include the affected username and leak source. Add session token status and credential access level if your IAM provides it.

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

Automate routine response through your SOAR platform:

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 gathered context for analyst review

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.

Method 4: Manual Spot Checks

Sometimes targeted manual checks make sense.

When manual checking is appropriate:

• Executive credential monitoring for high-value targets
• Investigating specific threat intelligence about your organization
• Verifying credentials for employees leaving the company
• Due diligence during M&A activities
• Incident response when you suspect credential compromise

For these targeted checks, use domain-based searches against credential monitoring APIs. Query specific email addresses or domain patterns on demand. Useful when you need answers fast rather than waiting for automated alerts.

The key is knowing when automated monitoring handles the workload versus when human judgment needs to guide the investigation.

What Should You Do When Compromised Credentials Are Found?

Finding leaked credentials means nothing if you don’t reset them fast.

Immediate Response Actions

Force a password reset immediately. Don’t send a friendly reminder. Disable the old password and require a reset on next login. For high-risk accounts, disable the account entirely until the reset completes.

Check authentication logs. Look for signs the credential was already used. Unusual login times or unfamiliar locations indicate active compromise. So does impossible travel. Search for the account’s authentication history for at least the past 30 days.

Review the leak source. The source determines response scope:

• Third-party breach credentials may be months old with limited fresh risk
• Infostealer-sourced credentials are high-risk and indicate an infected device
• Private forum credentials suggest targeted collection against your organization

Assess the blast radius. Does the credential access sensitive systems? VPN access, cloud admin consoles, production databases. Assume those systems may be compromised. Investigate accordingly.

Verify MFA status. Check whether the compromised account has MFA enabled. If not, enable it immediately. If MFA was enabled but session tokens were also leaked, the attacker may have bypassed it already.

Prioritization Framework

Not all leaked credentials carry equal risk. Prioritize based on potential impact:

Critical (respond in less than 1 hour):

• Domain admin or cloud admin credentials
• VPN access with session tokens
• Any credential with MFA bypass tokens
• Fresh infostealer logs (less than 72 hours old)
• Service accounts with elevated privileges

High (respond in less than 4 hours):

• Developer accounts with code repository access
• Finance and HR systems with sensitive data
• SSO credentials for critical applications
• Credentials with plaintext passwords
• IT staff accounts

Medium (respond in less than 24 hours):

• Standard employee accounts
• SaaS application access
• Email-only credentials from older breaches
• Accounts with active MFA protection

Low (batch processing):

• Former employee accounts (verify disabled)
• Credentials from breaches over 2 years old
• Accounts already protected with hardware MFA
• Test or sandbox accounts

When Credentials Come from Infostealers

Infostealer-sourced credentials require expanded investigation. A password reset isn’t enough because the employee’s device is likely still infected.

Launch an endpoint investigation to determine:

• What malware is present and whether it’s still active
• What other credentials were captured from that device
• Whether session tokens allow access even after password reset
• Whether lateral movement occurred from the compromised device
• What data the malware may have exfiltrated beyond credentials

Check for and terminate all active sessions for the compromised account. Modern infostealers capture session cookies and authentication tokens that let attackers bypass MFA entirely. Even after you reset the password, stolen cookies may still work.

The IBM X-Force report noted that credential harvesting occurred in 29% to 46% of incidents across industries in 2024. Many of these involved infostealers that captured far more than just passwords.

For detailed breach response procedures, see our guide on account takeover prevention.

Long-Term Remediation

After handling the immediate threat, address the root causes.

Review password policies. If the same passwords keep appearing in breaches, your policy may be too weak. Consider password length requirements over complexity rules. Block commonly used passwords and previously breached passwords.

Implement credential hygiene training. Employees who appear repeatedly in credential leaks need targeted education. Cover password reuse risks and phishing recognition. Hammer home why unique corporate passwords matter.

Deploy continuous monitoring. One-time checks aren’t enough. Implement ongoing credential monitoring that alerts your team whenever new exposures appear. The faster you know, the faster you can respond.

Strengthen endpoint protection. If infostealer infections are driving credential leaks, your endpoint security may need improvement. Ensure EDR solutions detect credential theft behavior, not just known malware signatures.

How Do You Measure Credential Security Over Time?

Checking credentials once accomplishes little. You need ongoing measurement to track improvement and prove your program’s value.

Time from detection to reset: How quickly does your team force password resets after credential alerts? Track the median and 95th percentile. The goal is hours, not days. If your average response time is measured in weeks, your monitoring investment is wasted.

Monthly exposure rate by source: How many credentials surface each month, and from where? Track breaches separately from infostealers. Rising infostealer numbers might indicate an endpoint security problem worth investigating. Decreasing numbers after training suggests your program is working.

Recidivism rate: Which employees appear repeatedly in credential leaks? Repeat offenders usually have poor security hygiene. They’re reusing passwords across personal and corporate accounts. They may need targeted training or tighter access restrictions.

Coverage metrics: What percentage of your domains are being monitored? How many users fall under your credential checking program? Complete coverage means no blind spots. If you only monitor your primary domain but have dozens of subsidiaries, you’re missing exposure.

Exploitation rate: Of the compromised credentials you detect, how many were already used before you caught them? This tells you if your detection is fast enough. If attackers keep beating you to the punch, you need faster sources or better integration.

Reset compliance rate: When you force password resets, how quickly do users comply? Track the percentage of users who reset within 24 hours versus those who take weeks. Users who delay create extended windows of vulnerability.

Track these metrics over time. They’ll show whether your program is actually reducing risk or just generating alerts.

Conclusion

Credential theft is accelerating. Stolen credentials accounted for 16% of intrusions in 2024, up from 10% the year before (M-Trends 2025). The attackers logging into your network with valid passwords won’t trigger your intrusion detection or fire your security alerts. They’ll look like legitimate users until they don’t.

Checking for compromised credentials isn’t a one-time project. It’s an ongoing operational requirement. Build Active Directory auditing into your quarterly reviews. Deploy dark web monitoring for continuous visibility. Integrate alerts into your SIEM and automate response through SOAR. Measure time to reset and track exposure trends.

The organizations that catch compromised credentials early reset passwords before exploitation. The organizations that don’t find out during incident response.

Breachsense monitors infostealer marketplaces and dark web forums for your credentials. Learn how compromised credential monitoring catches exposed passwords before attackers do.