What is Static Application Security Testing (SAST)?

Static Application Security Testing (SAST) or static code analysis detects application vulnerabilities by scanning the source code, byte code, or binaries of an application. By analyzing code patterns, control flows and data flows within an app, SAST can identify a range of vulnerabilities without running the application.

How does Static Application Security Testing (SAST) work?

SAST works by inspecting the source, binary, or byte code of an application and looking for code patterns that indicate common vulnerabilities. This is accomplished by creating a model of the application and code and data flows. Based on this model, the SAST solution can run predefined rules to identify known types of vulnerabilities.

Why is SAST an important security activity?

SAST solutions enable developers to “shift security left” by performing vulnerability analysis earlier in the software development lifecycle (SDLC). This enables developers to identify and fix vulnerabilities sooner, decreasing the cost of remediation and their potential impacts.

SAST also enables developers to receive more real-time feedback on the quality of their code. Instead of vulnerabilities only being identified and fixed at the end of the development process when a release candidate is ready, SAST scans can be performed after every code update. This helps developers to learn from their mistakes and develop more secure code in the future.

Pros and cons

SAST scanning solutions are invaluable for identifying common vulnerabilities. Some of the main advantages of SAST include:

• Early Appearance in SDLC: SAST does not require executable code, which allows it to be performed earlier in the SDLC. This reduces the cost and time requirements of fixing any identified vulnerabilities.
• Detection of Common Vulnerabilities: SAST solutions can identify the code patterns associated with common vulnerabilities such as those described in the OWASP Top Ten and Common Weakness Enumeration (CWE) lists.

Despite its benefits, SAST is not a perfect solution. Some limitations of SAST scans include:

• Being Language-Specific: SAST reads and analyzes an application’s source code, meaning that it needs to understand the language that it is written in. This can be problematic if an organization uses many different languages or less common ones.
• The Inability To Detect All Vulnerabilities: SAST solutions are designed to analyze source code, not a running application. This leaves it blind to configuration errors and runtime vulnerabilities.
• High False Positive Rates: SAST solutions do not perform runtime analysis, meaning that they cannot determine whether a potential vulnerability is a real threat or a false positive. SAST results must be analyzed to determine whether they represent real security risks.
• Frequent, Time-Consuming Tests: SAST scans take a long time to run, and the report analyzes a snapshot of the code so it becomes outdated quickly. This means that SAST scans must be run frequently to remain up-to-date.

SAST vs. DAST

Dynamic application security testing (DAST) analyzes a running application for potential vulnerabilities by sending various types of inputs to the application. DAST complements SAST, and some of the primary differences between the two approaches include:

• White-box vs. Black-box Testing: SAST solutions have complete visibility into an application’s source code. DAST solutions test a running application’s security with no visibility into its internal operations.
• Application Maturity: SAST scans are performed on source code or a binary and don’t require a running application. DAST solutions require the application to be complete enough to execute.
• Phase in SDLC: SAST’s use of source code enables it to be performed earlier in the SDLC than DAST, which requires access to an executable program.
• Cost of Remediation: SAST’s presence earlier in the SDLC enables it to correct vulnerabilities more cheaply than DAST. The later in the SDLC a vulnerability is discovered, the more code that might require remediation and the less time to do so.
• Detected Vulnerabilities: SAST solutions do not analyze running code, so they can’t identify runtime vulnerabilities or configuration issues. DAST solutions test running applications and can find these types of errors.
• Vulnerability Location Detection: SAST can identify the precise line of code where a vulnerability is located. DAST can only report that a particular vulnerability exists within an application.
• False Positive Rates: SAST solutions are more prone to false positives because they work based on a model of an application rather than running it. DAST solutions can tell if a particular vulnerability actually exists.

Improving Application Security with SAST

SAST is an invaluable tool for application security, and, complemented with DAST, can enable an organization to identify and remediate vulnerabilities in their applications before they are exploited by an attacker. Check Point AppSec provides a third vital component, protecting applications in production cloud environments. By monitoring requests to an application in context, AppSec can learn to identify what is legitimate traffic to an application and block attempted attacks.