Avoiding Common Mistakes in ASP-Based Applications

ASP Websites Common Mistakes Avoid Techhyme

ASP (Active Server Pages) has been a foundational technology for web application development for many years. While it offers great flexibility and ease of use, it’s crucial to understand and implement best practices to ensure the security and performance of your ASP-based applications. One of the most significant mistakes in ASP-based applications is the misuse of include files, which contain core application logic.

In this article, we will explore some essential practices to avoid common pitfalls and enhance the robustness of your ASP applications.

1. Renaming Include Files

Include files often contain sensitive logic and code that should remain private. To protect this content from view, it’s essential to rename any files with a “.inc” extension to “.asp.” By doing this, the IIS (Internet Information Services) engine will parse the include file and keep everything between the `<%` and `%>` tags private.

2. Server.HTMLEncode for User Input

When displaying user-supplied input in the browser, always use the `Server.HTMLEncode` method. This ensures that potentially harmful characters, such as `<` or `>`, are rendered innocuous. This practice is crucial in preventing cross-site scripting (XSS) attacks and can be used in conjunction with the `Response.Write` method.

3. Server.URLEncode for Database Input

Before passing data to a database, use the `Server.URLEncode` method. This precaution safeguards against malicious characters like apostrophes or semicolons that could potentially manipulate SQL queries. Sanitizing input data is vital for preventing SQL injection attacks.

4. Session Management

Proper session management is crucial for maintaining the security and usability of your ASP-based application:

  • Use the `Session.Abandon` method to explicitly end a user’s session when they log out.
  • Set an appropriate session timeout value that aligns with your application’s needs. E-commerce applications may benefit from a shorter timeout (e.g., 30 minutes), while intranet systems can have longer timeouts (e.g., 9 hours).

5. Response.Charset for Character Set Control

To reduce the risk of cross-site scripting attacks, use the `Response.Charset` method to force a specific character set for the rendered page. This ensures that a specific HTTP content-type header is present and enforces character encoding standards.

6. Session.SessionID as a Pseudo-Random Number Generator

Leverage the `Session.SessionID` object as a good pseudo-random number generator. However, be aware that session IDs are still susceptible to replay attacks unless their timeout threshold is set to an appropriate low value.

7. Error Handling

Handle errors gracefully by not providing users with the output of the `ASPError` object. Instead, return a polite, generic message to users and write the `ASPError.*` information to a log file accessible only to developers. This approach prevents exposing potentially sensitive information to malicious users.

8. Secure Database Connection

Use COM+ objects to broker database connection credentials. Never store the database username and password within ASP code, even if it’s enclosed within `<%` and `%>` tags. Keeping credentials separate from the application code enhances security.

9. Avoid String Concatenation in SQL Queries

Avoid crafting SQL queries with string concatenation, as it can lead to SQL injection vulnerabilities. Instead, use stored procedures to execute database operations. This practice enhances code readability, maintainability, and security.


In the world of web application development, security and best practices are paramount. By adhering to these guidelines and understanding the potential pitfalls of ASP-based applications, you can build robust, secure, and efficient web applications that provide a seamless experience for users while keeping sensitive data protected from threats. Whether you’re working with ASP scripts in Visual Basic, C++, or C#, these principles remain relevant and essential.

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