Application Security Best Practices

Without encryption, data transmitted over networks can be intercepted, read, and modified by attackers through man-in-the-middle attacks. Transport Layer Security (TLS) provides confidentiality, integrity, and authentication for network communications. Even within private networks and container orchestration environments, TLS should be used to protect against lateral movement by attackers who have gained initial access. The National Institute of Standards and Technology provides comprehensive guidance on TLS implementation.¹²

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Cryptographic controls protect data confidentiality and integrity when information is stored or processed. Weak or deprecated algorithms can be exploited by attackers with sufficient computational resources, potentially exposing sensitive data even when encryption was applied. Applications must use cryptographic algorithms approved by NIST for protecting sensitive data, following the guidelines for algorithm selection and key management.¹³¹⁴

Identity verification is the foundation of access control. Compromised credentials remain a leading cause of security breaches, with attackers using stolen passwords, credential stuffing attacks, and social engineering to gain unauthorized access. Proper authentication implementation includes secure password handling, multi-factor authentication for sensitive operations, and robust session management. Authentication mechanisms must follow current NIST Digital Identity Guidelines, which have evolved significantly to reflect modern threat landscapes and usability research.¹⁵

Applications receive data from many sources: user input, APIs, databases, files, and external services. Any data originating outside the application's trust boundary must be treated as potentially malicious. Injection attacks exploit insufficient validation to execute unintended commands, access unauthorized data, or compromise system integrity. SQL injection,¹⁶ cross-site scripting,¹⁷ and command injection¹⁸ remain prevalent attack vectors despite being well-understood. All data crossing trust boundaries must be validated, and input validation failures are consistently among the most exploited vulnerability classes.¹⁹²⁰

Web applications face unique threats due to their exposure on public networks and interaction with untrusted clients through browsers. Attackers exploit browser behaviors, cross-origin requests, and client-side state to perform attacks that traditional network security cannot prevent. Security headers instruct browsers to enforce protections, cookies require specific attributes to prevent theft, and cross-origin policies must be carefully configured. Web applications require additional security controls beyond general application hardening to address these browser-specific attack vectors.

Security vulnerabilities discovered late in development or after deployment are significantly more costly to remediate than those found early. Shifting security testing left in the development lifecycle enables teams to identify and fix issues before they reach production. Multiple testing approaches provide defense in depth: static analysis examines source code without execution, dynamic analysis tests running applications, and composition analysis identifies vulnerabilities in dependencies. Integrate security testing throughout the development lifecycle to catch vulnerabilities at every stage.²⁷

Prevention controls will eventually fail, making detection and response capabilities essential. Comprehensive logging provides the forensic data needed to investigate incidents, identify attack patterns, and demonstrate compliance with security requirements. Without adequate logging, organizations cannot detect ongoing attacks, understand their scope, or learn from security incidents. However, logs themselves can become a security risk if they contain sensitive data. Security-relevant events must be logged for incident detection and response while carefully excluding credentials and other sensitive information.²⁸

Credentials, API keys, database passwords, and cryptographic keys are high-value targets for attackers. Secrets committed to version control, hardcoded in source code, or stored in plaintext configuration files are routinely discovered through automated scanning and repository analysis. Once exposed, secrets can provide immediate access to production systems, databases, and cloud infrastructure. Proper secrets management involves secure storage, controlled access, regular rotation, and audit logging. Credentials and cryptographic keys require careful handling throughout their lifecycle to prevent unauthorized disclosure.²⁹