Cyberattacks grow every year. According to IBM’s Cost of a Data Breach 2024 report, the average cost of a data breach reached $4.88 million globally. This scenario requires companies to rethink how they develop software. Security can no longer be treated as an additional layer applied at the end of the process, it needs to be present from the first line of code.
Secure coding is the practice of developing software with resistance to vulnerabilities from the beginning of the development cycle. Instead of only thinking about functionalities, each architecture and implementation decision considers possible security breaches. At NextAge, we’ve applied these best practices for 18 years in all projects we develop for our clients, and we’ve gathered some of what can be applied in this article.
What is secure coding?
Secure coding means writing code that prevents known vulnerabilities through specific techniques, standards, and tools applied throughout development. While traditional development focuses first on making the system work and then worrying about security, secure coding integrates protection from conception.
This care extends throughout the entire software development life cycle (SDLC). From planning, where security requirements are identified, to maintenance, when updates fix vulnerabilities discovered after release.
Why is secure coding essential for your business?
Security in code protects the most valuable asset of modern companies: data. With LGPD (General Data Protection Law) in effect in Brazil and similar regulations in other countries, security failures can result in fines reaching up to 2% of the company’s annual revenue. Beyond legal penalties, there’s the operational cost.
The Ponemon Institute demonstrated in its 2023 study that fixing a vulnerability during production costs 30 times more than fixing it during development. This difference occurs because problems detected late require rework across multiple system layers, extensive testing, and coordination of emergency deployments.
Business continuity also depends directly on software security. Ransomware that paralyzes systems can cost millions in lost revenue, not to mention the impact on the supply chain and customers. At NextAge, we develop systems that keep operations protected through consistent security practices, applied in our modern Staff Augmentation services, Software Management Services, or Adaptive scope projets.
Main vulnerabilities that secure coding prevents
Knowing common vulnerabilities helps understand where to concentrate protection efforts.
- SQL Injection happens when an attacker inserts database commands through input fields.
- Cross-Site Scripting (XSS) allows malicious JavaScript code to be executed in other users’ browsers. This can steal session cookies, redirect to fake sites, or modify displayed content.
- Memory leaks occur when the program allocates memory during execution without releasing it afterward. Over time, the system consumes all available resources and crashes.
- Insecure deserialization happens when converting external data (such as JSON or XML) into internal objects without adequate validation.
- Insecure Direct Object References (IDOR) expose sequential IDs that allow guessing other users’ resources.
- Directory traversal allows navigating through the server’s folder structure through relative paths like “../”.
These vulnerabilities are listed in the OWASP Top 10, the ranking of the most critical threats in web applications regularly updated by the security community.
Secure coding best practices
1) Data validation and sanitization
Every input coming from users, external APIs, or files needs to be verified before being processed. Validation confirms if the data is in the expected format: an email contains “@”, a CPF has 11 digits, a date follows the correct pattern.
Sanitization removes or escapes dangerous characters. If someone types “<script>alert(‘xss’)</script>” in a name field, the system should remove HTML tags or convert them to plain text. This cleaning should always happen on the server, never trusting only browser validations that can be easily circumvented.
When displaying data to the user, use mechanisms that prevent code execution. Modern frameworks like React already do this automatically when rendering variables, but care is needed when using features that allow direct HTML.
2) Strict access control
The principle of least privilege determines that each user or system should have only the permissions necessary to execute their tasks. A finance employee doesn’t need to access HR data.
Multi-factor authentication (MFA) adds layers of protection beyond passwords. Even if credentials leak, the attacker still needs the second factor, usually a temporary code on the phone or a security token.
Role-based access control (RBAC) organizes permissions into logical groups. Instead of configuring access individually for 100 employees, you create roles like “manager,” “analyst,” and “auditor,” each with their specific permissions.
3) Third-Party code verification
Libraries and frameworks accelerate development but can introduce vulnerabilities. The State of Software Security report showed that 79% of applications contain at least one security flaw in third-party components.
Audit project dependencies regularly. Tools like npm audit, Snyk, or OWASP Dependency-Check identify known vulnerabilities in the libraries you use. Pin specific versions instead of accepting automatic updates that can break functionalities or introduce problems.
4) Use of modern languages and tools
Modern languages incorporate security features that prevent entire classes of vulnerabilities. Rust, for example, verifies memory usage at compile time, eliminating problems like use-after-free and buffer overflow that affect C and C++.
For projects that don’t require fine memory control, languages with garbage collection like Java, C#, or Go simplify resource management. TypeScript adds type checking to JavaScript, reducing errors that can create security breaches.
Static code analyzers examine source code for problematic patterns even before execution. SonarQube, Checkmarx, and SAST (Static Application Security Testing) tools integrate into the development pipeline and block commits that introduce known vulnerabilities.
Automate code reviews. Each pull request should pass through automatic security checks before manual approval. This ensures consistency and frees the team to focus on more complex aspects during review.
5) Proper error handling
Detailed error messages help developers diagnose problems but deliver valuable information to attackers. A message like “Error connecting to MySQL database on port 3306” reveals technology, configuration, and possible attack vectors.
Show generic messages to end users: “An error occurred. Please try again later.” Technical details should only go to internal logs, accessible only by the development and operations team.
These logs need care too. Never log passwords, authentication tokens, or sensitive personal data. Configure alerts for suspicious patterns: multiple failed login attempts, access outside business hours, or abnormally large requests.
Monitor logs actively. Tools like Splunk, ELK Stack, or Datadog aggregate information from multiple systems and facilitate real-time incident detection.
6) Encryption and data protection
Passwords should never be stored in plain text. Use hash functions designed for this purpose, such as bcrypt, scrypt, or Argon2. These algorithms are intentionally slow, making brute force attacks difficult.
Sensitive data at rest, stored in databases or files, needs encryption. AES-256 is the current standard for symmetric encryption, offering robust protection with acceptable performance.
Communication between client and server should always use HTTPS, which encrypts data in transit. Modern SSL/TLS certificates (TLS 1.3) ensure that no one intercepts or modifies information during transmission.
Manage cryptographic keys carefully. Never include them directly in source code. Use specialized services like AWS KMS, Azure Key Vault, or HashiCorp Vault to store and rotate keys securely.
How NextAge implements secure coding
With 18 years of experience in software development, NextAge integrates security in all project phases. Our approach begins in requirements analysis, where we identify sensitive data, critical flows, and exposure points.
During development, we systematically apply the practices described in this article. Code reviews include specific security checks. Automated tests validate not only functionalities but also behavior in the face of malicious inputs.
In our staff augmentation services, our team works integrated with the client’s team, sharing knowledge about secure coding. This strengthens the security culture within the contracting organization.
For software management services, we conduct security audits on existing code, identifying and fixing vulnerabilities. We implement incremental improvements without compromising stability.
Adaptive-scope projects are developed from scratch following best practices from the first sprint. We choose modern technologies, configure CI/CD pipelines with security checks, and document architectural decisions related to data protection.
Need systems developed with the highest security practices? Talk to our experts here.
