Leaked Credentials: What They Are and How to Protect Your Organization

Leaked credentials are everywhere. They’re traded on dark web forums, sold in underground marketplaces, and shared freely in criminal channels.

According to IBM’s 2025 Cost of a Data Breach Report, breaches involving stolen credentials cost $4.67 million on average and take 246 days to identify and contain.

Here’s what you need to know about leaked credentials, how they get exposed, and what to do when your credentials appear on the dark web.

What Are Leaked Credentials?

When most people think of leaked credentials, they picture usernames and passwords. But a modern credential leak includes much more:

• Usernames and passwords: The most common type, used to access accounts across websites and services
• Session tokens and cookies: These bypass multi-factor authentication entirely, letting attackers hijack active sessions
• API keys and access tokens: Used to access applications and cloud services programmatically
• Security questions and answers: Used for account recovery and often reused across multiple sites
• OAuth tokens: Grant access to connected applications without needing the original password

The scope of credential leaks has expanded dramatically. Attackers no longer need your password if they can steal your session token instead.

Why Is a Credential Leak Such a Serious Threat?

The numbers tell the story. According to IBM’s 2025 Cost of a Data Breach Report, breaches involving stolen or compromised credentials cost organizations $4.67 million on average. That makes credential-based attacks one of the most expensive breach types.

What makes this worse? Most organizations don’t even know their credentials are compromised.

IBM’s research shows it takes an average of 246 days to identify and contain a credential-based breach. That’s over 8 months of attackers having free access to your systems.

Here’s why a credential leak is so dangerous:

Password reuse multiplies the damage. Most people use the same password across multiple accounts. When one set of credentials leaks, attackers test them everywhere. A single leaked password can compromise your email, banking, corporate VPN, and cloud storage.

Infostealer malware has exploded. Modern infostealers harvest credentials directly from browsers and applications. They grab saved passwords, intercept credentials as you type them, and steal session cookies. One infection can leak hundreds of credentials from a single device.

Session tokens bypass MFA. Multi-factor authentication doesn’t help when attackers steal session tokens. They don’t need to authenticate. They hijack your already-authenticated session. This is why browser cookie theft has become a favorite technique.

Credentials are cheap and plentiful. A set of working corporate credentials can sell for as little as $10 on dark web marketplaces. Combo lists containing millions of username-password pairs trade for even less. The barrier to entry for attackers has never been lower.

What Types of Credentials Get Leaked?

Some leaked credentials are far more valuable than others. Understanding what attackers target helps you prioritize your defenses.

Usernames and passwords remain the most common. These come from data breaches, phishing attacks, and infostealer malware. Attackers use credential stuffing to test these passwords across other sites, exploiting password reuse.

Session tokens and browser cookies have become increasingly valuable. When an infostealer grabs your active session cookie, attackers can impersonate you without ever knowing your password. They simply import the cookie and pick up where you left off. MFA won’t stop this.

API keys and access tokens give attackers programmatic access to your infrastructure. A leaked AWS key can spin up crypto miners on your account. A leaked GitHub token can access private repositories. These often appear in public code repositories, configuration files, and developer forums.

Security questions and answers seem harmless but enable account recovery attacks. Mother’s maiden name, first pet, childhood street. These answers rarely change and often appear in multiple breaches.

OAuth tokens provide persistent access to connected services. They let attackers maintain access even after you change your password. Many people don’t realize how many third-party apps have OAuth access to their accounts.

How Does a Credential Leak Happen?

Understanding how credential leaks happen helps you defend against the most common attack vectors.

Infostealer malware is the primary source of exploitable credentials today. These aren’t sophisticated targeted attacks. They’re mass-distributed through fake software downloads, pirated programs, and phishing emails. One infection captures every credential you enter or save in your browser, plus session cookies and autofill data. The stolen data uploads to attacker servers within minutes. According to M-Trends 2025, stolen credentials now account for 16% of initial infection vectors, up from 10% in 2023.

What makes infostealers particularly dangerous is the quality of credentials they capture. These aren’t old passwords from 2015 breaches. They’re current, working credentials with active session tokens. Attackers can use them immediately.

Third-party data breaches contribute millions of leaked credentials annually. When a company gets breached, your credentials leak too. You might have perfect password hygiene, but if LinkedIn, Adobe, or Dropbox gets hacked, your credentials are exposed. Most people have accounts at dozens of services. Each one is a potential source of credential leaks.

Phishing attacks trick users into entering credentials on fake login pages. Sophisticated phishing kits capture not just passwords but MFA codes and session tokens in real-time. Attackers register lookalike domains, craft convincing emails, and intercept credentials as users type them.

Credential stuffing uses previously leaked credentials against new targets. Attackers take username-password pairs from one breach and test them across hundreds of other services. With password reuse rates above 60%, these attacks succeed more often than you’d expect. Even a 1-2% success rate means thousands of compromised accounts from a single credential leak containing millions of records.

Exposed databases and misconfigurations leak credentials through carelessness. Elasticsearch instances without authentication. MongoDB databases exposed to the internet. S3 buckets with public access. These misconfigurations expose millions of records before anyone notices.

Social engineering manipulates people into revealing credentials directly. Attackers impersonate IT support, executives, or trusted vendors. They create urgency and authority to bypass normal security instincts. A convincing phone call or email can get someone to hand over their credentials directly.

Insider threats come from employees with legitimate access. Disgruntled workers may deliberately leak credentials. Well-meaning employees may accidentally expose them through poor data handling. The threat from inside is often harder to detect than external attacks.

What Do Attackers Do With Leaked Credentials?

Leaked credentials fuel a broad range of criminal activities. Here’s what attackers do once they have your credentials.

Account takeover is the most direct use. Attackers log into your accounts, change passwords, and lock you out. They access personal information, financial data, and anything else stored in the compromised account. From there, they can impersonate you, steal funds, or pivot to other targets.

Financial fraud follows quickly. Compromised banking credentials lead to unauthorized transfers. Leaked payment card data enables fraudulent purchases. Attackers drain accounts, apply for loans in your name, and sell financial access to other criminals.

Business email compromise uses compromised email accounts to trick employees into making wire transfers. Attackers monitor email threads, learn payment patterns, and insert themselves into conversations. Attackers using a compromised executive email account can authorize millions in fraudulent payments before anyone notices.

Ransomware deployment often starts with leaked credentials. Attackers use valid VPN or RDP credentials to gain initial access. From there, they move laterally through the network, disable security tools, and deploy ransomware. The initial credential compromise might have happened months earlier.

Lateral movement extends the damage. One set of credentials leads to another. Attackers use compromised accounts to access shared drives, internal systems, and other users’ data. A single leaked password can eventually provide access to the entire network.

Dark web resale turns credentials into cash. Fresh credentials sell for premium prices. Bulk credentials from major breaches sell cheaper but in massive quantities. Criminal marketplaces specialize in different credential types, from streaming accounts to corporate VPN access.

Corporate espionage targets trade secrets, intellectual property, and competitive intelligence. State-sponsored attackers and criminal groups both use leaked credentials to infiltrate companies and steal valuable information.

How Can You Detect Leaked Credentials?

You can’t protect what you don’t know is compromised. Detection is the critical first step.

Dark web monitoring scans criminal marketplaces, hacker forums, and data dump sites for your organization’s credentials. Effective monitoring covers not just public breach databases but private infostealer channels where fresh credentials first appear. This is where compromised credential monitoring provides the most value.

Log analysis can reveal credential compromise after the fact. Look for impossible travel patterns, login attempts from unusual locations, and access during off-hours. Multiple failed authentication attempts followed by success often indicate credential stuffing.

Threat intelligence feeds provide context about active credential threats. They identify which credential dumps are circulating, which infostealers are active, and which organizations are being targeted.

Endpoint detection can catch infostealer infections before credentials leak. Modern EDR tools recognize infostealer behavior patterns and can stop credential theft in progress. This is proactive defense rather than reactive detection.

How Should You Respond to Leaked Credentials?

When you discover leaked credentials, speed matters. Every hour of delay gives attackers more time to use your credentials.

Immediately reset compromised passwords. Don’t wait. Force password resets for all affected accounts. Make sure new passwords are strong and unique. Consider using a password manager if you don’t already.

Revoke active sessions. Changing the password isn’t enough if attackers have session tokens. Force re-authentication by invalidating all active sessions. This kicks out anyone using stolen session cookies.

Enable or strengthen MFA. If the compromised accounts didn’t have multi-factor authentication, enable it now. If they did, consider whether attackers might have compromised MFA tokens as well.

Investigate the scope. Determine how credentials were leaked. Was it an infostealer infection? A phishing attack? A third-party breach? Understanding the source helps you prevent recurrence and identify other potentially compromised accounts.

Monitor for follow-on attacks. Leaked credentials often precede larger attacks. Watch for unusual activity on related accounts, lateral movement attempts, and signs of persistent access. Attackers may have established backdoors before you detected the compromise.

Notify affected parties. If customer or partner credentials were exposed, tell them quickly. It’s the right thing to do, and many regulations require it. Be clear about what happened and what you’re doing to fix it.

Document and learn. Record what happened, how you responded, and what worked. Use this to improve your security and respond faster next time.

How Can Organizations Prevent a Credential Leak?

Prevention beats response every time. Here’s how to stop credential leaks before they happen.

Deploy password managers across your organization. Unique, strong passwords for every account eliminate the password reuse problem. Users only need to remember one master password. Everything else gets generated and stored securely.

Implement phishing-resistant MFA. Not all MFA is equal. SMS codes can be intercepted. TOTP apps can be phished in real-time. Hardware security keys and passkeys provide the strongest protection against credential theft. CISA recommends phishing-resistant MFA for all critical accounts.

Strengthen endpoint protection. Infostealers are the primary source of leaked credentials. EDR tools that detect and block infostealer behavior prevent credential theft at the source. Keep endpoints updated and don’t let users install random software.

Train employees to recognize threats. Phishing and social engineering succeed because people aren’t prepared. Regular security awareness training, combined with simulated phishing tests, helps employees spot attacks before they click.

Monitor continuously. Credential security isn’t a one-time project. Dark web monitoring should run continuously, alerting you when your credentials appear in new breaches or infostealer logs. Early detection enables faster response.

Segment network access. Limit the damage from any single compromised credential. Zero trust architecture ensures that one compromised account can’t access everything.

Audit third-party access. Review which services have OAuth tokens and API access to your systems. Revoke unnecessary permissions. Monitor for unusual third-party activity.

Prepare your response plan. When credentials leak, you need to act fast. Document your response procedures before an incident. Know who makes decisions, who executes the response, and how you’ll communicate with affected parties.

The threat from leaked credentials isn’t going away. Infostealers keep improving. Dark web marketplaces keep growing. Organizations that detect and respond quickly limit the damage. Those that don’t give attackers more time to exploit their access.

Take the first step. Check if your credentials are already exposed on the dark web.