Best Practices for Securing Full Stack .NET Applications
Securing a .NET application requires protecting code, APIs, data, networks, identities, and deployment pipelines. The goal is to ensure confidentiality, integrity, and availability across the entire stack.
This guide is divided into:
Backend (.NET API Security)
Frontend Security
Database & Data Protection
Authentication & Authorization
Infrastructure Security
DevOps & CI/CD Security
Logging, Monitoring & Incident Response
1. Backend Security (ASP.NET Core API)
✔️ Use HTTPS Everywhere
Enforce HTTPS redirection in ASP.NET Core (UseHttpsRedirection()).
Use HSTS to prevent protocol downgrade attacks.
✔️ Enable Authentication & Authorization Middleware
Always use:
app.UseAuthentication();
app.UseAuthorization();
✔️ Validate and Sanitize Inputs
Use Model Validation ([Required], [StringLength], etc.).
Use defensive coding against injection attacks.
✔️ Protect Against Common Web Attacks
Enable built-in ASP.NET Core anti-forgery tokens for state-changing requests.
Enable rate limiting (ASP.NET Core 7+ built-in).
Use data annotation validation and server-side validation.
✔️ Secure API Endpoints
Use attribute-based policies:
[Authorize(Roles = "Admin")]
Apply least privilege for all operations.
✔️ Limit Data Exposure
Never expose domain models directly.
Use DTOs to control outgoing data.
Avoid returning full exception details to clients.
2. Frontend Security (Angular / React / Blazor)
✔️ Protect Against XSS
Avoid using innerHTML blindly.
Angular and React automatically escape output—do not bypass this.
✔️ Use HttpOnly & Secure Cookies
Store sensitive tokens in HttpOnly cookies, not localStorage.
✔️ Implement CORS Safely
Only allow specific origins.
Set limited allowed headers and methods.
✔️ Disable Browser Auto-Complete for Sensitive Forms
<input autocomplete="off">
3. Data & Database Security
✔️ Use Parameterized Queries or ORM
Using EF Core prevents SQL injection by default.
Never build SQL strings manually.
✔️ Encrypt Data
Encrypt sensitive data at rest (SQL Server Transparent Data Encryption).
Use Always Encrypted for ultra-sensitive columns.
✔️ Secure Connection Strings
Use Azure Key Vault, AWS Secrets Manager, or environment variables.
Never store secrets inside appsettings.json.
✔️ Limit Database Permissions
Follow least privilege:
Application users should not be DB admins.
Use separate accounts for read/write operations.
4. Authentication & Authorization
✔️ Use Modern Identity Protocols
Recommended:
OAuth2.0
OpenID Connect
Azure AD / IdentityServer
✔️ Store Passwords Securely
If using ASP.NET Core Identity:
Passwords are automatically hashed using PBKDF2.
Always enforce password policies.
✔️ Token Security
Use short-lived access tokens (JWT).
Use refresh tokens with revocation and rotation.
✔️ Multi-Factor Authentication (MFA)
Add MFA wherever possible.
Support authenticator apps (Microsoft Authenticator, Google Authenticator).
5. Infrastructure Security
✔️ Use Firewalls & Network Segmentation
Separate public API, private services, and databases.
Use WAF (Web Application Firewall) for web apps.
✔️ Secure Cloud Infrastructure
For Azure / AWS / GCP:
Enable DDOS protection.
Enforce private endpoints for databases.
Use Managed Identities instead of secrets.
✔️ Patch and Update Regularly
Keep .NET runtime, dependencies, and OS updated.
Automate dependency checking with tools like Dependabot or Renovate.
6. DevOps & CI/CD Security
✔️ Secure the CI/CD Pipeline
Use least privilege for CI runners.
Avoid storing secrets in pipelines.
Use secrets vaults for tokens and passwords.
✔️ Static Code Analysis
Use:
SonarQube
GitHub Advanced Security
dotnet analyzers
These catch vulnerabilities before deployment.
✔️ Signed Builds
Code signing ensures binaries are not tampered with.
7. Logging, Monitoring & Incident Response
✔️ Use Structured Logging
Serilog, NLog, or built-in .NET logging.
Include correlation IDs to track requests across services.
✔️ Enable Security Logging
Authentication failures
Authorization failures
Unusual access patterns
Exception logs
✔️ Centralize Logs
ELK stack (Elasticsearch, Logstash, Kibana)
Azure Application Insights
Seq / Splunk
✔️ Enable Alerting
Trigger alerts on:
Suspicious admin activity
Token replay attempts
Repeated 401/403 responses
8. Summary Checklist
Area Best Practice
API Security HTTPS, input validation, rate limiting
Authentication OAuth2 + JWT + MFA
Authorization Role & policy-based access control
Data Protection Encryption at rest & in transit
Secrets Never stored in code; use vaults
Infrastructure Firewalls, private networks, updates
Frontend Prevent XSS, secure CORS
DevOps Signed builds, static analysis, secure CI/CD
Monitoring Centralized logs + alerts
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