Credential stuffing is an account takeover attack in which cybercriminals use stolen usernames and passwords—typically obtained from previous data breaches—to gain unauthorized access to customer accounts. By automating login attempts at scale, attackers exploit password reuse across multiple services, often targeting online accounts that contain valuable personal, financial, or loyalty program data.

For airlines and other customer-facing organizations, credential stuffing can lead to unauthorized bookings, loyalty point theft, account compromise, fraud, and loss of customer trust.

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How credential stuffing works

Attackers use automated tools to test large volumes of stolen credentials against login portals, mobile applications, and customer service platforms. Because many users reuse passwords across multiple sites, a single compromised credential pair can provide access to multiple accounts.

Modern credential stuffing campaigns are highly automated and can generate significant login traffic, making it difficult to distinguish malicious activity from legitimate user behavior.

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Why credential stuffing matters

Credential stuffing attacks can create substantial business and customer impacts, including:

• Account takeover and unauthorized access
• Loyalty program fraud and theft of rewards
• Exposure of personal or sensitive information
• Financial losses from fraudulent transactions
• Increased customer support and remediation costs
• Brand and reputation damage
• Regulatory and compliance risks

Organizations with large customer bases are particularly attractive targets because of the scale and value of customer account data.

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Reducing credential stuffing risk

Effective defense requires a layered security strategy that combines identity, application, and infrastructure protections.

Key best practices include:

• Enabling multi-factor authentication (MFA)
• Encouraging strong, unique passwords
• Monitoring for abnormal authentication activity
• Implementing rate limiting and access controls
• Using behavioral analytics to identify suspicious login patterns
• Conducting regular security assessments
• Securing APIs and customer-facing services

Organizations should also educate users about password reuse and encourage the use of password managers to improve credential hygiene.

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How DigiCert can help

Credential stuffing attacks often generate large volumes of automated traffic that can cause significant strain on customer-facing services and supporting infrastructure.

DigiCert UltraDNS provides secure, resilient, enterprise-grade DNS services that help organizations maintain the availability and performance of critical digital services. With globally distributed infrastructure, intelligent traffic management, DNSSEC protection, and built-in resilience against large-scale attacks, UltraDNS helps ensure customers can reliably access online services even during periods of elevated malicious activity.