Definition

static application security testing (SAST)

Contributor(s): Kate Brush

Static application security testing (SAST) is a program designed to analyze application (app) source code in order to find security vulnerabilities or weaknesses that may open an app up to a malicious attack. Software developers have been using SAST for over a decade to find and fix flaws in app source code early in the software development life cycle (SDLC), before the final release of the app.

How does SAST work?

SAST is a white box testing method, meaning it analyzes an application from the inside, examining source code, byte code and binaries for coding and design flaws, while the app is inactive. A SAST scan can occur early in the SDLC because it does not require a working application or code being deployed.

Since SAST can occur early in the SDLC, it can provide developers with real time feedback, allowing them to resolve issues with the code before it is passed on to the next step of the SDLC. However, it is important to note that SAST tools must be used on a regular basis to ensure vulnerabilities are caught anytime the app undergoes a daily/monthly build or code is checked or released.

Besides being used with mobile and web applications, SAST tools can be applied to code in embedded systems and other locations.

The majority of SAST tools are compatible with leading industry compliances like:

  • payment card industry data security standard (PCI DSS)
  • health insurance portability and accountability act (HIPAA)
  • and motor industry software reliability associations (MISRA)

When using SAST tools, it is important that they support both the language -- like Java or Python -- and the application framework. If the SAST tool is not compatible with the language and framework, then obstacles and blocks may occur during testing.

Key steps to run SAST effectively

In order for SAST to perform effectively, organizations that build applications with different languages, frameworks and platforms should observe the following steps:

  1. Choose the proper SAST tool. The tool should be compatible with the programming language so that it can perform code reviews of applications written in the respective language. The tool should also understand the underlying framework the company’s software uses.
  2. The scanning infrastructure is created and the tool deployed. This involves handling the licensing requirements, setting up access control and authorization and obtaining the necessary resources -- like servers and databases to deploy the tool.
  3. Customize the tool to suit the needs of the business. For instance, a company might configure it to find additional security vulnerabilities by writing new rules or updating current ones. The configurations made could reduce the possibility of false positives by writing new rules. A false positive is when a test result wrongly lists a security vulnerability, displaying the flaw as present when it is not. SAST tools are also integrated into the app's build environment with the creation of dashboards and custom reports.
  4. When the tool is ready, the applications are assigned to the test. Organizations with a large number of apps should prioritize the high-risk ones and scan them first. After onboarding all the applications, scan them on a regular basis and sync the scans with release cycles, daily or monthly builds or code check-ins.
  5. Once the test is complete, analyze scan results to remove false positives. After the issues are finalized, they should be tracked and handed off to the deployment teams for remediation.

Throughout this process, it is important to properly train and oversee the development team to guarantee they are using the SAST tools appropriately. The test should be included in the app development and deployment processes.

Benefits of SAST

SAST can help evaluate both server-side and client-side security vulnerabilities. The test helps developers find vulnerabilities in the early stages of the development process, allowing them to immediately fix any issues and prevent additional costs or problems caused by dealing with issues at the end. The real time feedback provided by the test allows flaws to be removed before moving further along in the SDLC, helping prevent security issues from becoming an afterthought.

SAST tools can be automated and integrated into a project's development environment, allowing developers to monitor their code regularly. The test can provide graphical representations of discovered flaws, making the code easy to navigate. Some tools even point out the exact location of vulnerabilities and highlight the faulty code. This advantage can provide thorough guidance on how to fix problems as well as direction to the best place in the code to fix them.

SAST tools can scan 100% of the codebase and they can do it much faster than humans performing secure code reviews. SAST tools can scan millions of lines of code in minutes and automatically identify key vulnerabilities, including SQL injection (SQLi), cross-site scripting (XSS) and buffer overflows, improving the overall quality of the code that’s being developed. By tracking all the security vulnerabilities found by the test, developers can fix the flaws quickly and release the application with the smallest amount of issues.

Another benefit of SAST is its ability to help verify a developer's compliance with coding guidelines and standards without deploying the underlying code. SAST tools can also be used by scrum masters and product owners to regulate security standards within their development teams and organizations, allowing for increased code integrity and faster reduction of vulnerabilities.

Challenges of SAST

SAST tools can be complicated and difficult to use as well as incapable of working together. Each different SAST tool focuses only on one area of potential vulnerabilities. SAST tools can also be hard to execute since they must be integrated into the SDLC in order to find flaws prior to the deployment of the apps.

Furthermore, while the close look at an app's source code can be beneficial, SAST tools cannot identify vulnerabilities outside of the code, leaving room for external flaws, such as weaknesses that could be discovered in a third party interface.

Another challenge created by SAST is the involvement of false positives. This error is both annoying and time consuming since it forces developers to trace and analyze the code in order to separate the false positive results from the accurate ones.

Importance of SAST

The increasing amount of data breaches has led organizations to pay more attention to their application security. The biggest advantage that organizations have over hackers and other attackers is the ability to access an application's source code. SAST uses this advantage to delete vulnerabilities in the early stages of development. Introducing SAST into the SDLC can improve the quality of the developed code since the tools automatically discover critical weaknesses like SQL injection and cross-site scripting.

Furthermore, the amount of developers in an organization frequently outnumbers the amount of security staff. This disadvantage makes it difficult for organizations to complete code reviews on even the smallest amount of applications. SAST tools allow all of the applications and codebase to be analyzed. SAST assists organizations in automating the security process and helps them produce a secure SDLC, enabling quick and accurate solutions to flaws and vulnerabilities as well as consistent improvements of the code's integrity.

SAST vs. DAST

For comprehensive security testing, SAST is often used with dynamic application security testing (DAST). While SAST is a white box testing method and analyzes an app from the inside, pinpointing exactly where vulnerabilities are found, DAST is a black box testing method. DAST evaluates the app from the outside, launching fault injection techniques to discover threats.

SAST discovers vulnerabilities early on in the SDLC and DAST uncovers flaws and weaknesses at the end. As a result, it is less expensive to fix vulnerabilities found through SAST than DAST. SAST is also able to support all software and perform with all types of SDLC methods. DAST usually only scans apps -- especially web apps and web services -- and works best with the waterfall model.

One advantage that DAST has over SAST is the former's ability to discover run time and environment related issues. DAST tools are also less likely to report false positives. Furthermore, DAST can understand arguments and function calls, allowing it to determine if a task is acting as it should. SAST is unable to check calls and usually cannot check argument values either.

Finally, SAST can be automated and integrated into the SDLC, alleviating the inconvenience created by testing apps for security. DAST requires a special infrastructure to be created for large projects. For DAST to be successful, special tests must be performed and several samples of the app running in parallel with other input data must be given.

This was last updated in June 2019

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