Appsec Knowledge Center

SAST Best Practices and More – How To Secure Source Code

7 min.

SAST Hero image

Static Application Security Testing, otherwise known as SAST, is a methodology where source code is analyzed to uncover security vulnerabilities which may open your organization up to risk. Using the SAST methodology, static code analysis tools scan applications before the code has been compiled or executed to find these vulnerabilities and shore up your defenses before a threat can be leveraged by an attacker. This article will explain SAST in greater detail, discuss the impact of source code attacks, and take a broad look at secure coding and Static Application Security Testing best practices. 

Why do Organizations Need SAST?

When organizations ask themselves how to secure source code, SAST is often one of the first answers they come up with. As SAST identifies security vulnerabilities early in the software development lifecycle, organizations don’t need to wait until something goes wrong before they make changes to code. This ‘shift left’ style of security avoids reputational damage and limits rework, and supports a strong security posture where application vulnerabilities can be caught early before they can cause a breach. 


As developers don’t want security slowing them down, they often love SAST’s ability  to help them improve the quality of their source code, quickly identifying common errors and vulnerabilities to ensure stability earlier in the cycle, without security becoming a blocker to innovation and speed  SAST is also a tool that helps the business align application standards with a number of compliance regulations — and is therefore critical for any organization that handles sensitive information or is aware of the growing risk of a data breach.

The Effects of Source Code Attacks

Let’s take a step back and think about why source code vulnerabilities are so important to protect against in the first place. When attackers steal or alter source code, they can cause unlimited business disruption and damage, including: 


  • Intellectual property exposure: Source code can contain some of an organization’s most critical assets, including proprietary algorithms, designs and plans, and even trade secrets. This can give a competitor a leg up, or provide leverage for a malicious attacker to exploit a company even further. 
  • Data leakage: By manipulating and stealing your data, a source code leak can lead to sensitive data exposure — especially devastating in industries such as Healthcare, Legal or Finance. This can have a domino effect on regulatory compliance, reputation, and customer trust. 
  • Supply chain attacks: Source code attacks can have a continuing downstream effect. If your software vulnerabilities are exposed, the clients who depend on your services could be the next target from there. Attackers often use application vulnerabilities to target your own customers. 
  • Financial cost: The impact of a data breach through a source code attack hits the bottom line hard. This could be anything from regulatory action and decreased sales, to increased customer churn, or the struggle of building back your reputation with partners and investors. 

Common Source Code Risks

To keep the impact of application vulnerabilities at bay, many organizations are turning to SAST, as well as static code analysis tools and broader secure coding tools. When making a static application security testing checklist, include secure coding tools and processes as well, and think about the following risks, and how your strategy will work to prevent them: 


    • Dataflow problems: Data that originates from an insecure source needs to be validated and cleansed before it is used. 
    • Semantic errors: Code should be analyzed in context, for example detecting SQL injections, and ensuring all syntax and identifiers are examined and tokenized. 
  • Misconfigurations: All application configurations should be checked and validated to align with business-specific policies.
  • Control flow: Are there any dangerous sequences in place, such as secure cookie transmission failures, misconfigurations, or uninitiated variables that could suggest cross-site scripting (XSS)?
  • Structural flaws: Risks here include inconsistencies in language-specific code structures, weaknesses in class design and use of variables and functions, and hardcoded password generation.
  • Memory problems: In this category, think about additional data issues such as buffer overflows which attackers can use to change execution paths. Vulnerable functions such as print, strcat, and strcpy can be identified and flagged here, too. 

Top Tips for How to Secure Source Code 

OWASP has published secure coding practices that can support any organization in getting ahead of source code risks and application vulnerabilities. 


The list starts with input validation, where all users test the data for anything that could cause the application to act in an anomalous way. This could be done using data validation techniques that compare data against a list of allowed characters or a baseline, such as comparing header data to ASCII characters for example. All data should be validated, including embedded code, HTTP headers, and URLs. OWASP also recommends output encoding, where unverified or unsafe data is translated, and it does not execute as code, preventing cross-site scripting attacks. Instead, all characters are encoded until they are considered to be secure. 


As part of a strong security posture, authentication and password management is always critical. OWASP has a number of techniques for password management, including preventing the re-use of passwords, reporting login failures to the user, and setting a password complexity policy across the organization. Next, session management is important to help manage multiple requests from a web application from different users. Best practices include terminating sessions on logout, ensuring each User ID can only log in once concurrently, and reducing the session inactivity timeout feature. Another helpful application security best practice is to lean on least privilege for access control, database security and data protection, so that only authorized users have access to crown jewel assets and data. For data protection, don’t forget to exclude sensitive data from GET requests found in HTTP, as well as excluding the autocomplete feature for passwords and usernames. 


As encryption is a critical element of data security, OWASP suggests cryptographic practices so that data can remain confidential. Organizations should use a random number generator, and secure cryptographic key management. Communication security also focuses on encryption, suggesting using Transport Layer Security (TLS) to safeguard sensitive information over external sources and to protect connections, specified with character encoding. When connections fail — OWASP dictates that they shouldn’t auto-downgrade to unsecure protocols. 


There’s no such thing as source code without errors and bugs. Error handling and logging is therefore really important, so you can keep track of changes, authentication attempts, and any unexpected changes, and retain debugging information for future reference without storing sensitive data. 


Finally, OWASP delves into system configuration, and file and memory management. All systems and their components need to be up to date with patches and version upgrades, and HTTP response headers should not include OS, versions and framework details. Test and dev environments should be isolated from production. For file management, authentication and validation processes need to be structured, and best practices such as never sending the absolute file path to the client need to be followed. For memory management, check buffer size for overflows, avoid vulnerable functions, and truncate input strings before using copy and concatenation functions. 

 Protect Your Applications with Checkmarx and Software Application Security Testing Best Practices

As part of Checkmarx One, our leading application security testing solution, Checkmarx offers robust SAST, to help you scan against application security risks at the earliest possible stage, and implement source code best practices. With Checkmarx One, SAST becomes an integral part of the software development lifecycle, allowing your organization to align security testing with quality testing, and shift left on application vulnerabilities and source code errors at the earliest possible stage and shift everywhere throughout the entire SDLC, from code-to-cloud. 


Our adaptive vulnerability scans are quick and powerful, identifying the greatest risks to the business, and uncovering the true root of a vulnerability so you can make a change where it will have the greatest impact. Checkmarx SAST scans immediately on check-in, directly from source code repositories, including GitHub, GitLab, Azure and Bitbucket. 


From the scan, Checkmarx provides developers with best-fix locations of where and how to fix the vulnerability — zooming in to the specific line of code, alongside guided steps for remediation. You can also use our AI query builder to fine tune your SAST queries, without being an expert in the query language, and improve the fidelity of your results, reducing false positives and tailoring searches with the power of GenAI. When vulnerabilities are exposed, AI auto remediation explains the vulnerability in natural language, and can provide the exact code snippet to fix it. 


As the platform is integrated with the Integrated Development Environment (IDE), as well as build management tools, bug tracking, and source repositories, developers can access and fix source code issues without leaving the flow of their day-to-day tasks. 


With Checkmarx One, SAST becomes a powerful enabler, securing applications at the coding stage, and minimizing vulnerabilities already in the source code. Built with developers in mind, teams can prioritize their activities where it will impact and reduce business risk, and deliver more secure applications with the peace of mind of knowing they have quality source code in place. 

Looking to shift left and uncover the critical vulnerabilities in your application source code? Book your demo of Checkmarx One.