Leaked Credentials Detection: Finding Exposed Passwords
Credential Monitoring Data Breach Dark Web Monitoring
Where Do Leaked Corporate Credentials Appear? Corporate credentials leak through multiple channels. Security teams need …
Learn how to detect compromised employee credentials before attackers use them to breach your network.
• Infostealer malware now accounts for most fresh corporate credential leaks, harvesting passwords within hours of infection.
• Checking for compromised credentials requires monitoring dark web markets, stealer logs, and private forums continuously.
• Leaked session tokens let attackers bypass the login and MFA requirement entirely.
• Infostealer-sourced credentials indicate an infected endpoint, not just a leaked password.
Your employees’ credentials are probably circulating on the dark web right now. IBM X-Force found that 30% of intrusions in 2024 used valid account credentials as the initial access vector (IBM X-Force 2025). Attackers aren’t breaking in. They’re logging in.
The fastest-growing source of corporate credential exposure 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 accounted for 16% of initial infection vectors in 2024, up from 10% in 2023 (M-Trends 2025). And less than 41% of organizations consistently reset credentials after phishing incidents (SpyCloud 2025). That gap between credential theft and password reset is where breaches happen.
This guide covers how security teams check for compromised credentials across their organization, what to do when you find them, and how to prevent credential compromise in the first place.
Contents
What Are Compromised Credentials?
Compromised credentials are authentication data that attackers have stolen. This includes more than just passwords.
Compromised credentials are authentication data that attackers have stolen. This includes usernames, passwords, session tokens, and API keys exposed through breaches, infostealers, or phishing.
Types of compromised credentials include:
- Passwords and password hashes from third-party breaches
- Session tokens stolen by infostealers that let attackers bypass MFA
- API keys and access tokens leaked in code repositories
- MFA bypass codes captured during phishing attacks
- SSO credentials that unlock access to multiple corporate applications
The distinction between “compromised” and “leaked” matters for response. Leaked credentials appeared in a breach somewhere. Compromised credentials are actively being traded or used by attackers. Treat both as urgent, but compromised credentials from fresh stealer logs need immediate action.
How Do Employee Credentials Get Compromised?
Understanding how credentials leak helps you prioritize detection. Different sources require different response playbooks.
Infostealer malware:
Infostealers like LummaC2, RedLine, and Raccoon capture credentials as employees type them. They steal passwords saved in browsers, session tokens, and autofill data. IBM X-Force reported an 84% increase in infostealers delivered via phishing in 2024 (IBM X-Force 2025). When an employee’s device gets infected, every credential they access from that device gets exfiltrated and sold within days.
Stealer logs are what malware exports after infecting a device. They contain stolen passwords, session tokens, screenshots, and browser data. Fresh logs hit criminal marketplaces within 24-72 hours.
Third-party breaches:
When sites your employees use get breached, those credentials leak too. If an employee reuses their corporate password on LinkedIn and LinkedIn gets breached, that password is now exposed. Over 35% of breaches in 2024 originated from third-party compromises (SecurityScorecard 2025).
Phishing attacks:
Phishing remains effective because it harvests credentials directly. Attackers create convincing login pages for corporate SSO, VPN portals, and cloud services. Advanced phishing kits capture session tokens in real-time, giving attackers authenticated access even after the employee closes the fake page.
Password reuse:
Employees reusing corporate passwords on personal accounts create a risk you can’t control. When that personal service gets breached, attackers test those credentials against corporate VPNs and SSO portals. Credential stuffing attacks automate this process across thousands of accounts in minutes.
How Do You Check If Your Organization’s Credentials Are Compromised?
Checking for compromised credentials at enterprise scale requires monitoring multiple sources continuously. Individual email checks don’t cut it when you’re protecting thousands of employees.
Method 1: Domain-based dark web monitoring
Monitor all your corporate email domains across dark web markets, stealer marketplaces, and private forums. When credentials containing @yourcompany.com appear, you get alerted. This catches exposures from both breaches and stealer logs.
Dark web monitoring platforms cover sources that aren’t publicly accessible. Criminal marketplaces like Russian Market and 2easy specialize in selling corporate access. Telegram channels trade fresh credentials daily. Private forums require trust scores to access.
Method 2: Executive and high-value target monitoring
Prioritize monitoring for accounts with elevated access. Domain admins, cloud admins, finance, and executives need extra attention. Attackers target these accounts because they provide broader access.
Set up alerts specifically for VIP email addresses and their known personal accounts. Executives often get targeted by spear phishing campaigns and their credentials fetch premium prices on criminal markets.
Method 3: Third-party breach monitoring
Track breaches at services your employees use. When a SaaS vendor gets breached, check if any employees registered with corporate emails. Password reuse means a LinkedIn breach could compromise your Okta access.
Monitor vendor security news and breach disclosure sites. Subscribe to threat intelligence feeds that track emerging breaches before they hit the mainstream news.
Method 4: Integration with identity systems
Connect your credential monitoring to your IAM and SSO systems. When compromised credentials surface, automated workflows can force password resets immediately. This cuts the time between detection and response.
For critical accounts, configure automatic account lockout when high-confidence alerts trigger. Lower-risk exposures can queue for review without blocking access.
What Should You Do When You Find Compromised Credentials?
Detection means nothing without response. Here’s what to do when your monitoring catches exposed credentials.
Immediate response steps:
Force a password reset immediately. Don’t send a friendly reminder. Disable the old password and require a reset on the next login.
Check authentication logs. Look for signs the credential was already used. Unusual login times, unfamiliar locations, or impossible travel patterns indicate an active compromise.
Identify the leak source. Third-party breach credentials may be months old with limited exposure. Infostealer-sourced credentials are fresh and high risk.
Terminate active sessions. Password resets don’t invalidate existing sessions. Revoke all active tokens for the affected account.
Assess the blast radius. If the credential provides access to sensitive systems, assume those systems may be compromised.
For infostealer-sourced credentials:
When credentials come from infostealers, you have a bigger problem than a leaked password. The employee’s device is infected. Everything accessed from that device may be compromised. Investigate the endpoint, check for lateral movement, and figure out what else the infostealer captured.
Session tokens matter as much as passwords:
Modern infostealers don’t just capture passwords. They exfiltrate session tokens too. An attacker with a valid session token can access accounts without triggering login prompts or MFA challenges. They look like a legitimate authenticated user.
If the leak includes session data, terminate all sessions and require re-authentication. Check recent activity for signs of session hijacking. Attackers often use stolen session tokens within minutes of purchase.
For detailed response procedures, see our guide on what to do when passwords are exposed in a breach.
How Do You Prioritize Credential Alerts?
Alert fatigue kills credential monitoring programs. Not all exposed credentials carry equal risk.
Risk triage factors:
| Factor | Higher Risk | Lower Risk |
|---|---|---|
| Account type | Domain admin, cloud admin, VPN | Standard user, former employee |
| Leak source | Fresh stealer logs | Old breach (2+ years) |
| Leak contents | Session tokens, plaintext password | Hashed password, MFA enabled |
| Account status | Active, recent logins | Dormant, disabled |
| MFA status | No MFA, SMS MFA | Hardware token, FIDO2 |
Response tiers:
Critical (respond in < 1 hour): Domain admin credentials, VPN access with session tokens, cloud infrastructure accounts. Disable immediately and investigate.
High (respond in < 4 hours): Developer accounts with code repository access, finance systems, HR systems with PII. Force reset and review recent activity.
Medium (respond in < 24 hours): Standard employee accounts, SaaS application access, email-only credentials from old breaches. Queue for password reset.
Low (batch processing): Former employee accounts (verify disabled), credentials from breaches over 2 years old. Document and include in weekly report.
How Do You Prevent Credential Compromise?
Detection catches credentials after they leak. Prevention reduces how many leak in the first place.
Deploy MFA everywhere:
CISA recommends phishing-resistant MFA like FIDO2 or PKI-based authentication for high-value accounts. Even basic MFA limits what attackers can do with stolen passwords. Prioritize VPN, SSO, cloud consoles, and any system with sensitive access.
Catch infostealers at the endpoint:
Your EDR should detect common infostealer families. But infostealers evolve rapidly. Configure detection for credential theft behavior, not just known malware signatures. Look for browser credential access and keylogging patterns. These catch more than signature matching alone.
Consolidate authentication through SSO:
Every application where employees create accounts with corporate email accounts is another breach waiting to happen. Fewer credentials means a smaller attack surface. NIST’s Digital Identity Guidelines recommend consolidating authentication where possible. SSO reduces the number of passwords employees manage and lets you see all login activity in one place.
Train employees on phishing:
Phishing bypasses technical controls by harvesting credentials directly from users. Regular training and simulated phishing campaigns reduce success rates. Focus on recognizing fake login pages, suspicious URLs, and unexpected authentication requests.
Monitor for password reuse:
Some credential monitoring platforms can identify when corporate passwords appear in non-corporate breach data. That means employees are reusing passwords across personal and work accounts. Flag these users for targeted security training.
Conclusion
Checking for compromised credentials isn’t optional for enterprise security. IBM X-Force found attackers used valid credentials in 30% of intrusions in 2024. When attackers have valid passwords, they’re not breaking in. They’re logging in.
Effective credential checking requires continuous monitoring across dark web markets, infostealer channels, and private forums. Point-in-time checks miss the fresh credentials that pose the greatest risk. You need monitoring that catches exposures within hours, not weeks.
The window between credential theft and exploitation keeps shrinking. Your detection and response need to move faster than attackers.
For enterprise-grade credential detection that covers stealer marketplaces and dark web combo lists, learn how compromised credential monitoring protects your organization before attackers log in as your employees.
Compromised Credentials FAQ
Compromised credentials are authentication data that attackers have stolen. This includes usernames, passwords, and session tokens exposed through breaches, malware, or phishing. For enterprises, this means corporate VPN passwords, SSO credentials, and session tokens that let attackers bypass MFA entirely.
Watch for unusual login activity like off-hours access, unfamiliar locations, or impossible travel patterns. MFA prompts you didn’t trigger and password reset emails you didn’t request are red flags. Dark web monitoring often catches credentials before attackers exploit them.
Three main vectors: infostealer malware on employee devices harvests passwords as they’re typed, third-party services your employees use get breached, and phishing attacks trick employees into entering credentials on fake login pages. Infostealers are growing fastest because they capture credentials within hours of infection.
That 80% figure comes from the Verizon 2022 DBIR, but it specifically refers to basic web application attacks, not all breaches. For all breach types, credentials are involved in 22-31% of incidents. IBM X-Force 2025 found credentials used in 30% of intrusions. The percentage varies by methodology, but credentials consistently rank as a top attack vector.
Enable MFA everywhere, preferably FIDO2 hardware keys for high-value accounts. Use a password manager instead of browser password storage. Never reuse passwords across sites. Deploy endpoint protection that catches infostealer malware. Monitor for leaked credentials continuously.
The three random words method, recommended by NCSC, creates passphrases by combining three unrelated words like ‘correct horse battery.’ This creates passwords that are long enough to resist brute force attacks while remaining memorable. Add numbers and symbols between words for extra strength.
