What is Dynamic Application Security Testing (DAST)?
It is a test that is done from an end-user perspective to detect malicious activities and attacks. In this, security test cases are performed during the application runtime. It helps to find the runtime issues of an application with lower possibilities of false positives as the request and response are analyzed as it is. It is also a part of BlackBox testing as the attacker or malicious user does not know anything about the application except the URL or application login interface.
Why is DAST Important?
The source code of an application is primarily confidential; therefore, most attackers target a web application in dynamic environments. Simulating those malicious attackers and compromised environments during DAST can help an organization find a bug before the application is released. Modern web application architectures also induce misconfigurations as not every developer is aware of them. With DAST, many security misconfigurations can be found and removed from the application.
Types of DAST
DAST can be divided into mainly two types, as given below.
The testing tool uses crawlers and the main URL to scan the application in automated DAST. The tool will also monitor and audit entire web applications to find critical vulnerabilities. Every accessed page in the application is logged along with its request and response from the server.
The automated DAST can be configured to check for denial of service and brute force attacks, too however it will slow the main application or website. Therefore, denial of service and brute force tests are generally made with the consent of the application owner.
In manual DAST, the testing is done related to the context of the application. An automated DAST scan cannot find all the vulnerabilities in the system. Business logic vulnerabilities are generally out of scope for automated DAST as the automated scan cannot be fine-tuned for every application. Therefore manual DAST is used.
The tester has to understand the application in depth which is in the testing scope, and then create test cases depending on various scenarios which can be breached by a malicious user. The request sent to the server can be genuine or a crafted one, and the response from the server is captured manually by proxy tools. Due to this, application-specific manual DAST can find critical vulnerabilities which cannot be found by automated DAST.
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What are the challenges of DAST?
DAST is a valuable testing tool that can uncover security vulnerabilities other tools can’t. Though DAST excels in certain areas, it does have its limitations. Let's look at the challenges.
Session management is too difficult as the cookies and tokens may be short-lived in the application. Once login is done, the login authentication tokens become valid only for some minutes. However, the DAST scan might take hours, depending on the functionalities and inputs in the application. Therefore after a token expires, DAST scan cannot test the rest of the functionalities.
A mechanism should be developed to refresh or re-authenticate with the application before the old token expires and use the new token for further requests.
Automated Privilege Escalation
Privilege escalation mechanisms in DAST scans are very rare as automated DAST scans test the application on a pre-defined methodology. Due to the complexity of privilege escalation depending on the application architecture, automated privilege escalation becomes non-existent.
DAST scanning should include automated scripts designed explicitly for privilege escalation in the context of an application that needs to be tested.
False Negatives and False Positives
Depending on payload signatures, the DAST scanning can declare a malicious attempt a false negative or declare a genuine user request a false positive. These false negatives and false positives increase proportionally with the size and user base of the application.
False positives can be removed using manual testing; however, false negatives are not detectable by DAST tools.
DAST tools cannot crawl every URL which is used in the application backend. Sometimes a single program method at the backend accepts one or more variables for different functionalities. Therefore, DAST tools cannot predict all the variables and their functionalities by themselves.
A manual crawl for each function is the only way to find all URLs related to their respective functionalities.
What are the Best Practices of DAST?
Following these best practices can ensure better identification, reporting, and fixing of security vulnerabilities
Collaboration with Developers
DAST acts as a feedback mechanism for developers. It tells developers about the loopholes in the application designed and developed by them. After a DAST scan is done, developers can use the results and modify their code concerning the vulnerabilities found. After modification, another DAST scan should be done until all the vulnerabilities are taken care of.
As developers become aware of their code's flaws, they start to develop secure coding practices. Vulnerable methods and logic flaws in programming become less. Unless a new type of threat orzero-day vulnerabilitydoes not come to light, secure coding acts as a foolproof defense against cyber attacks.
Integration with Multiple Platforms
Nowadays, applications are developed for multi-platform scenarios. A web application also has its mobile counterpart as well as APIs. A DAST scan should be done for all the versions and platforms of the application so that the application is secured from all angles.
Combination of Manual and Automated DAST: All the applications in which DAST has to be done should follow manual, and automated DAST approaches. Automated DAST can quickly find most of the vulnerabilities in the earlier testing phase. A manual DAST scan can remove the false positives found in automated DAST, as well as can find new vulnerabilities based on the application context, which cannot be tested by automated DAST.
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Various DAST tools used nowadays are given below.
It is a proxy tool used for detecting vulnerabilities in web and mobile applications. It is available in Enterprise, Professional, and Community editions. Enterprise and Community edition is mainly used commercially by international organizations, whereas the community version is a single-user free edition and has more minor functionalities. This tool is used for application scanning, bug bounty hunting, and research purposes.
This tool uses dynamic and interactive mechanisms to detect vulnerabilities in the application. Payload request signature testing and behavior testing a part of test cases performed by this tool. It also helps develop secure code practices as vulnerable codes are highlighted in the scans.
It performs automated security testing to prevent cyber attacks. Blackbox and Whitebox are both types of testing that can be done by this tool. It can also scan websites and applications to find embedded vulnerabilities.
This tool provides a managed DAST solution. A non-intrusive, zero-touch and cloud bases approach is followed by this tool for scanning the application. It also guarantees zero false positives and provides the scan report and the remediation steps that need to be taken.
Acunetix performs test cases related to OWASP Top 10, exposed databases, SQL injection, out-of-band vulnerabilities, XSS, security misconfiguration, etc. It crawls through every link on the application while detecting the vulnerabilities. Multi-level forms, HTML pages, SPA, etc., are all scannable by this tool. Trend graphs and WAF virtual patching are also supported by it.
This tool comes with four different versions used for different vulnerabilities, i.e. standard, source, enterprise, and cloud. The standard version is used for dynamic scanning of the application. The scan results by standard version are available in a report format with a priority-wise list of vulnerabilities found starting from the most critical one. Fix recommendations are also included in the report, which can help developers mitigate the vulnerabilities faster.
Checkmarx is used for multiple types of applications such as open-source, dynamic and static, interactive APIs, infrastructure as code, etc. Its IAST solution is considered a modern version of DAST scanning as it can be directly implemented in the quality assurance phase of the application and reduce most of the delays which happen in DAST scanning.
It provides a single platform for cloud security, SIEM, Application Security, vulnerability risk management, etc. Its product AppSec is a DAST scanning tool that can automatically assess modern web apps and APIs with low false positives. The scan report also includes the compliance part, and the DAST scan can be scaled for large application sizes.
DAST scans are essential in the ever-changing scenarios of cyber attacks. Doing DAST scan from the beginning helps secure the application in an early stage. A combination of automated and manual DAST scans provides overall security to the application. Multiple tools are available for DAST scan in the market. As a single tool cannot detect all the vulnerabilities in the application, DAST scan should be done with multiple commercial and open source DAST tools for better security.