C# Security Assessment and Testing

As the dependence on computers, the internet and software increases, so does the rate of cybercrimes. The total number of malware infections was 12.4 million in 2009, which increased to 816.2 million in 2019. That calls for one thing; extensive security testing and assessment of any and all pieces of software produced and deployed across the globe. 

C# is not only just a popular language for web and application development but also the go-to language for a lot of developers when it comes to portable advancement. Things like Strategy Pattern and Mediator Pattern in C# are keeping this language relevant even in 2021. That means the security of this language is of paramount importance. 

All Vulnerabilities are Liabilities

It is estimated that 90% of all cyberattacks exploit a vulnerability in the code of an application to compromise its security. To secure an application and its data, it is crucial to eliminate all such bugs and weaknesses. 

How to Secure C# Applications?

The most important thing about application security that all programmers need to understand is that security is not something to be thought of after the application has been developed. It needs to be a part of the development process from the very beginning. 

There are three main types of application security assessment and testing that can ensure that the code has no vulnerabilities that can be exploited to compromise the application’s security.


Static application security testing, or SAST, is the most primitive form of security testing. It incorporates testing and looking for vulnerabilities in a code at the earlier stages of the software development lifecycle. It makes sure that the code complies with the established security guidelines and has no known vulnerability even before it is executed for the first time. 


Dynamic Application Security Testing, or DAST, is employed to find weaknesses and security vulnerabilities in a running application. It accomplishes that by purposefully subjecting the application to fault injection. Typically, malicious data is fed to the application to discover common security vulnerabilities like cross-site scripting and SQL injection. 

DAST also allows developers to look for runtime errors in a code that cannot be analyzed on a static code. These include authentication, server configuration and other issues that surface only when a user logs in.

SAST and DAST Work Together 

SAST and DAST are primarily used in tandem. The reason being, none of the two is capable of comprehensive security testing on its own. SAST is incapable of identifying runtime errors and vulnerabilities, and DAST cannot flag errors in the lines of the code. 

SAST is extremely useful in pinpointing the errors in the code, and it can narrow the problem down to the exact line of code. For example, if a weak random number generation parameter is used, SAST can accurately diagnose it. However, when it comes to data flow flaws, SAST is not very efficient.  

SAST is also notorious for a high frequency of false positives and false negatives, and only DAST can be used to cross-check and determine which of the errors reported are correct.

Limitations of SAST and DAST 

SAST and DAST are good for establishing a baseline for securing code, but they cannot be relied upon for the complete security of a web-based application. They lack what it takes to secure the latest web and mobile applications. 

For example, the libraries and frameworks found in modern apps give SAST a hard time looking for vulnerabilities. That is mainly due to the reason that static testing tools are only able to scan the application code they can follow. 

Modern libraries can cause these tools to choke and produce “lost sink” and “lost source” messages. 

The solution? Interactive Application Security Testing or IAST. Before having a look at IAST, it’s essential to know how the testing is carried out.

Open Source Vulnerability Scanners are the Way to Go

All that security testing is not done manually. There are tools for that. Like any other software, application security testing tools are both open-source and closed source. 

Open source vulnerability scanning tools are a better option for securing C# apps. This is because any security testing tool is only as good as the database behind it. The databases of open source tools are updated by a lot of sources and with a high frequency. That translates to better security scanning and more reliable results, especially when securing an application for the latest threats.


IAST is formulated to mitigate and overcome the shortcomings of SAST and DAST. It takes the fundamental elements of both and adapts them for the modern development environment.

The way IAST works is by placing an agent within the source code of the application. The agent can then perform analysis on the application anywhere and anytime during the software development lifecycle.

As an IAST agent works inside the app, its analysis can be applied to the entire app. That means its runtime data flow information, HTTP requests and responses, configuration information, frameworks and other components, libraries, and even backend connection information.

As IAST has access to all those software components, it can cover more of the app’s code, give accurate results, and ensure the implementation of a broader range of security parameters than SAST or DAST.


The most important part of developing any application is making it secure. Application security needs to be a part of the software development lifecycle from the very start. The oldest approach to application security testing is Static Application Security Testing or SAST, with the newer ones being dynamic and interactive application security testing. All kinds of application security testing are carried out by application vulnerability scanner tools which are available as open-source or closed source. Open-source options are better as they have a broader database and are more efficient and effective in finding vulnerabilities in the code. 

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