Compromised Credentials: Causes, Examples, and Defensive Measures

What Are Compromised Credentials Attacks? 

Compromised credential attacks occur when a threat actor gains unauthorized access to a system by using valid login credentials, such as usernames and passwords. These attacks typically exploit stolen or leaked credentials obtained through data breaches, phishing scams, or malware infections. 

Cybercriminals use these compromised credentials to infiltrate systems undetected, posing a significant threat to organizational security and individual privacy.

The impact of these attacks extends far beyond unauthorized access. With access to an account, attackers can exfiltrate sensitive data, escalate privileges, or propagate malware across a network. Such breaches often result in financial losses, reputational damage, and legal liabilities for affected organizations. Understanding how compromised credential attacks work is crucial to implementing defenses.

This is part of a series of articles about insider threats.

The Dangers of Compromised Credentials

Once an attacker gains access using stolen credentials, they can operate with the same privileges as a legitimate user. This makes it difficult for traditional security systems to detect malicious activity, especially if multi-factor authentication is not in place. The attacker can blend into normal user behavior, remaining undetected for extended periods.

Compromised credentials are often a gateway to lateral movement across systems. An attacker may use initial access to locate and compromise higher-privileged accounts or sensitive databases. In many cases, they establish persistent access by creating new user accounts or installing backdoors, ensuring continued access even if the original credentials are revoked.

These attacks frequently lead to data breaches involving confidential customer information, intellectual property, or internal communications. The consequences include regulatory penalties, loss of customer trust, and significant recovery costs. In critical environments like healthcare or finance, the fallout can extend to operational disruption or public safety risks.

Credential compromise also enables ransomware deployment, where attackers encrypt files and demand payment. Alternatively, compromised accounts might be used to launch further phishing campaigns, impersonating trusted employees to deceive others within or outside the organization.

Common Causes of Compromised Credentials 

Phishing and Social Engineering

Phishing and social engineering attacks manipulate users into divulging sensitive information, such as login credentials, by exploiting trust or urgency. Attackers often impersonate trusted entities like banks or company executives to make their requests appear authentic. These scams are typically conducted via email, messages, or fake websites, designed to deceive users into willingly surrendering their credentials.

The success of phishing lies in the psychological manipulation of human behavior, bypassing technical safeguards. Whether through spear-phishing targeting specific individuals or widespread campaigns, these attacks are a leading cause of credential compromise. Employees and users must be trained to recognize these tactics and adopt caution in their interactions.

Keyloggers and Malware

Keyloggers and malware are malicious tools designed to capture user inputs or compromise systems. Keyloggers monitor and record keyboard strokes, enabling cybercriminals to harvest usernames, passwords, and other sensitive information. Malware, on the other hand, can gain access to stored password databases or browser credentials, making them vulnerable to theft.

Keyloggers are often installed covertly as part of phishing emails, malicious software downloads, or infected USB devices. Their stealthy nature means users may be unaware until significant damage has occurred. Implementing endpoint security and anti-malware solutions is critical to combatting this cause of compromised credentials.

Dark Web Marketplaces

Once credentials are stolen, they are often sold on dark web marketplaces. These online forums enable cybercriminals to trade stolen data, including login details, at relatively low costs. Buyers can then use these credentials for fraudulent activities like identity theft, financial scams, or further breaches, making dark web marketplaces a hub for cybercrime.

Stopping the cycle of credential exploitation requires monitoring the dark web for signs of stolen data and taking immediate action to secure any exposed accounts. Organizations must also invest in breach detection tools to reduce their vulnerability, alongside educating users about the risks of data breaches.

Credential Stuffing and Brute Force

Credential stuffing and brute force attacks attempt to exploit reused or weak passwords. Cybercriminals automate these attacks, testing thousands of stolen credentials across multiple platforms to identify accounts using the same password. Brute force attacks, in contrast, guess combinations of characters until the correct one is found, targeting accounts with weak password protections.

The success of such attacks is often due to poor password hygiene, such as using common phrases or reusing passwords across multiple sites. Enforcing strong password policies and using multi-factor authentication are effective measures to counter these threats, as they limit the viability of automated attempts.

Recent Examples of Compromised Credential Attacks 

A series of high-profile attacks in recent years illustrate the widespread threat posed by compromised credentials. Below are detailed examples:

• Duo Security (April 2024): Duo, a multi-factor authentication service owned by Cisco, suffered a credential stuffing attack that endangered the message logs of over 40,000 customers.
• Microsoft (Nov 2023 – Jan 2024): Microsoft disclosed that it had experienced a coordinated credential stuffing campaign over a three-month period. The attack was attributed to Midnight Blizzard (also known as Nobelium), a Russian state-sponsored threat actor.
• 23andMe (2023): The genetics company was hit by a credential stuffing attack that exposed around one million lines of customer data. Attackers used previously leaked credentials to gain access to user accounts, bypassing standard defenses through reuse of login information.
• Norton LifeLock (2023): Approximately 925,000 customer accounts were targeted in a credential-based attack against the cybersecurity provider. Attackers attempted to log in using credentials harvested from other data leaks.
• Okta (2023): A hacker used stolen credentials to infiltrate Okta’s customer support system, gaining unauthorized access to sensitive backend environments.
• PayPal (December 2022): Hackers obtained and exploited login credentials for 35,000 user accounts. Although PayPal reported no financial losses or unauthorized transactions, the breach forced the company to reset passwords and monitor affected accounts.

These incidents demonstrate that no organization is immune to compromised credential attacks and that security measures must include robust user authentication, monitoring, and rapid incident response protocols.

Tools and Techniques for Compromised Credentials Detection 

Breach Monitoring and Dark Web Scanning

Breach monitoring and dark web scanning tools continuously search public breach repositories and underground forums for stolen credentials. These tools compare discovered data with internal user credentials, alerting organizations when matches are found. This proactive detection enables rapid incident response—such as forcing password resets—before attackers can exploit the exposed credentials.

Security services like Have I Been Pwned, SpyCloud, and commercial threat intelligence platforms integrate automated alerts into security operations. Integrating breach monitoring into identity management systems helps limit the window of vulnerability caused by exposed accounts.

Endpoint Detection and Response

Endpoint detection and response (EDR) systems monitor activity on individual devices to identify suspicious behavior that may indicate the use of compromised credentials. For instance, if a device starts communicating with known malicious servers, installs unknown software, or accesses sensitive files unusually, EDR tools generate alerts.

EDR platforms also record historical endpoint activity, supporting forensic investigations. This visibility is critical when compromised credentials are used in combination with malware or to establish persistence through unauthorized tools or scripts.

User and Entity Behavior Analytics

User and entity behavior analytics (UEBA) solutions create behavioral baselines for users and systems, then detect deviations that may signal credential misuse. For example, if a user suddenly logs in from a new country or accesses large volumes of data outside normal working hours, UEBA flags this anomaly.

These systems enhance detection accuracy by correlating multiple behavioral signals, reducing false positives. UEBA is particularly effective at spotting insider threats and sophisticated attacks where compromised credentials are used in stealthy ways.

Security Information and Event Management

Security information and event management (SIEM) systems aggregate logs and events from across an organization’s infrastructure. They correlate authentication attempts, endpoint activity, and network traffic to detect signs of compromised accounts.

SIEM platforms support real-time alerting and automated workflows, enabling rapid containment of credential-based intrusions. They are also crucial in compliance reporting and post-incident analysis, helping teams understand attack vectors and refine future defenses.

5 Best Practices for Strong Credential Security 

1. Enforce Two-Factor Authentication

Two-factor authentication (2FA) provides an additional layer of security beyond a simple username and password. By requiring users to verify their identity with a second factor—such as a code sent to their phone, a hardware token, or a biometric check—organizations make it significantly harder for attackers to gain unauthorized access, even if credentials are compromised. This second factor creates a barrier that automated attacks like credential stuffing and brute force attempts cannot easily bypass.

Effective 2FA implementation should cover all access points, including VPNs, cloud services, and internal systems. It’s essential to enforce 2FA consistently, with no exceptions for high-privilege users who are frequent targets. User education and seamless integration with existing workflows help ensure adoption and reduce friction, while backup methods—like recovery codes—should be securely managed to prevent lockouts.

2. Implement Adaptive Authentication

Adaptive authentication strengthens access controls by dynamically assessing risk during login attempts. It evaluates contextual signals like geolocation, device fingerprint, IP reputation, and login time to determine whether additional verification is needed.

When anomalies are detected—such as a login from an unusual location or a new device—the system can prompt for multi-factor authentication or block access entirely. By responding to real-time conditions, adaptive authentication balances usability with heightened security, making it more difficult for attackers to exploit stolen credentials.

3. Implement Regular Credential Audits

Credential audits involve periodically reviewing and verifying user access rights, password practices, and account usage across systems. These audits help identify inactive accounts, redundant privileges, and outdated credentials that could become security liabilities.

Automated tools can assist in auditing by highlighting discrepancies such as multiple failed login attempts, outdated password hashes, or inconsistent access patterns. Immediate revocation of unused or unnecessary credentials is critical to reducing the attack surface. Additionally, enforcing the principle of least privilege ensures that users only retain the access necessary for their roles.

4. Provide Ongoing Security Awareness Training

Employees are often the first line of defense against credential-based attacks. Regular security training helps users recognize phishing attempts, avoid unsafe practices, and understand the importance of safeguarding credentials.

Training programs should include simulated phishing campaigns, updated threat examples, and clear protocols for reporting suspicious activity. Tailoring sessions to specific roles or departments increases relevance and engagement. Reinforcement through microlearning or monthly tips can maintain awareness over time.

5. Monitor for Anomalous Login Patterns

Effective monitoring involves continuously analyzing login activity for irregularities that may indicate compromised accounts. These include logins from multiple geographies within short time frames, excessive login attempts, or access to unusual resources.

Security operations centers (SOCs) should deploy automated detection tools to flag suspicious behavior for investigation. Integration with SIEM and UEBA platforms enhances visibility across the network, enabling faster threat detection and response. Alerts should be actionable, providing context like user behavior history and threat intelligence to support timely decisions.

Compromised Credential Protection with Exabeam

Exabeam’s UEBA engine in New-Scale Analytics is built to detect threats involving stolen or misused credentials by learning what normal behavior looks like for every user and system across the environment. You can deploy it as part of the full Exabeam New-Scale Fusion SIEM platform or use New-Scale Analytics independently to augment your existing SIEM. Rather than depending on static rules or predefined alerts, it continuously analyzes activity to identify deviations such as logins at unusual times, access to sensitive systems that were never touched before, or high-volume data transfers outside expected patterns. These behavioral anomalies help uncover attacks that blend in with legitimate access, including insider threats or external actors using valid login credentials.

The engine powers Smart Timelines that automatically reconstruct incidents without the need for manual log stitching which reduces menial tasks by 30%. Analysts benefit from a clear and contextual view of suspicious behavior, which helps reduce investigation time by up to 80%. By surfacing the most relevant threats and cutting out noise, Exabeam reduces alert fatigue by 60% and enables teams to detect and respond to incidents 50% faster compared to traditional tools.

In real-world use cases, compromised credentials are involved in the majority of serious breaches. According to Delta AIrlines, Exabeam helped identify credential-based attacks that had gone unnoticed for months. The platform analyzes behavior across all relevant data sources to catch these subtle threats early, even when there are no obvious indicators. Security teams using Exabeam have successfully responded to incidents within minutes, maintained service level agreements, and improved their ability to stop advanced threats before damage occurs.

To learn how Exabeam detects compromised credential attacks across any environment and enables faster response through behavioral analytics and automation, read this solution brief on compromise credentials. It includes real-world examples, key detection techniques, and best practices to strengthen your defenses today.

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