Threat Replay Testing: Turning Attackers into Pen Testers

API security is no longer just a concern; it’s a critical priority for businesses. With APIs serving as the backbone of modern applications, they’ve become a primary target for attackers. While automated security testing tools help detect vulnerabilities, their limitations leave organizations exposed to evolving threats. Here’s where Threat Replay Testing (TRT) comes into play. 

This cutting-edge approach flips the script, allowing security teams to turn real-world attack attempts into valuable insights for protecting API infrastructure. Below, we’ll break down what Threat Replay Testing is, how it works, and why it’s a game-changer for DevOps engineers, security professionals, and API developers. 

Why Traditional Testing Falls Short

To appreciate the value of Threat Replay Testing, it’s important to understand the limitations of conventional API security testing. Today, most organizations rely on automated security testing tools to scan their APIs. While broadly effective, these tools have limitations that could result in missed API vulnerabilities. 

Automated Security Testing Tools

Most organizations rely on automated tools to scan for vulnerabilities. While useful, these tools mainly test exposed endpoints and apply rule-based testing methods using predefined scenarios. This creates significant blind spots since:

• Hidden or underused APIs often go untested.
• Novel attack methods are not detected, as they fall outside the scope of known vulnerabilities.
• Regular updates and fine-tuning are required to keep pace with emerging threats.

Static Test Scenarios

Attackers don’t follow a script. They use adaptive techniques to bypass existing defenses. Static testing methods fail to replicate this dynamic behavior, leaving organizations vulnerable to innovative exploitations. 

Threat Replay Testing addresses these shortcomings by leveraging real-world data for dynamic testing, ensuring relevance and effectiveness against current attack methods.

Threat Replay Testing bridges the gap between theoretical security testing and real-world response. Unlike traditional methods that rely on predefined testing scenarios, TRT leverages real attack data to simulate potential vulnerabilities. 

Essentially, TRT identifies malicious requests intercepted by your security systems, analyzes their characteristics, and uses them to generate simulated test attacks. These test attacks mimic the original threats in a controlled and safe environment, enabling organizations to better understand their system vulnerabilities and proactively secure them before attackers can exploit them. 

By creating tests from real-life data, TRT evolves with attackers, offering dynamic defenses against constantly changing threats. 

How Threat Replay Testing Works

We must break down its process step by step to understand TRT’s capabilities. The following section illustrates how this method effectively identifies and mitigates vulnerabilities. 

1. Capturing Real Attack Data

TRT begins by collecting malicious request data from the Wallarm Filtering Node (or similar tools). These are requests flagged as potentially harmful in your production system. For instance, a detected SQL injection attack (SQLi) targeting a login endpoint provides the raw data that TRT uses to formulate test cases. 

This initial data includes:

• The attacked URL and endpoint
• The specific type of attack (e.g., SQLi, XSS)
• Parameters associated with the attack, such as payloads or tokens

2. Generating Test Cases

Using the collected data, TRT generates 100-150 test requests. Each is designed to target the same vulnerabilities as the captured malicious request but with a variety of payloads. These generated payloads simulate real attack behaviors while omitting any truly harmful code or syntax, ensuring the safety of your systems. 

For example, if the original malicious request attempted to manipulate the user parameter for SQL injection, test cases might include variations like:

• https://staging.example.com/login?user=UNION SELECT username, version() --
• https://staging.example.com/login?user=1' OR SLEEP(10)--
• https://staging.example.com/login?user=1")+AND+PG_SLEEP(5)--

3. Redirecting Test Requests

The replayed test requests are never sent to production systems. Instead, they are safely redirected to staging or development environments, where they cannot disrupt your live operations. This ensures that the simulated attacks remain purely exploratory and pose no risk to end-users or active applications. 

4. Analyzing System Responses

The module evaluates how your APIs respond to these simulated attacks. It identifies key vulnerability indicators, such as unexpected behaviors, server errors, or responses that suggest the attempt was partially successful. 

For every identified weakness, TRT logs details into a vulnerability dashboard like the Wallarm Console UI. This actionable data empowers your security team to act quickly and effectively to close gaps. 

The following diagram demonstrates how the TRT  works:

For detailed instructions on how to enable Threat Replay Testing and create test policies, please review the product documentation.

As APIs grow in number and importance, TRT can be the essential security measure that ensures APIs are free from vulnerabilities that attackers could exploit.

Threat Replay Testing in Action

Now let’s jump in to see an example how TRT would work in reality. The Threat Replay Testing module is designed to create test requests in the most secure manner possible, featuring the following key characteristics:

• Malicious payloads of generated requests do not include real malicious syntax, they are intended just to imitate the attack principle. As a result, they do not harm your resources.
• Authentication headers like Cookie, Authorization: Basic, and Viewstate are excluded from replayed requests. Further, as guided by the custom authentication headers and masking rule, any additional headers may be adapted or removed as required.

Step 1:Consider the following real-world-like GET request initially detected by the Wallarm filtering node and uploaded to the Cloud:

https://prod.example.com/login?user=UNION SELECT username, password

From the request, the module learns the following details:

• The attacked URL is https://prod.example.com/login
• The type of used attack is SQLi (according to the UNION SELECT username, password payload)
• The attacked query string parameter is user
• Additional piece of information provided in the request is the request string parameter token=IyEvYmluL3NoCg (it is probably used by the application to authenticate the user)

Step 2:Leveraging this data, the module crafts a series of test requests. These requests focus on potential SQL injection vulnerabilities using varied payloads, such as:

https://staging.example.com/login&user=1')+WAITFOR+DELAY+'0 indexpt'+AND+('wlrm'='wlrm
https://staging.example.com/login&user=1+AND+SLEEP(10)--+wlrm
https://staging.example.com/login&user=1);SELECT+PG_SLEEP(10)--
https://staging.example.com/login&user=1'+OR+SLEEP(10)+AND+'wlrm'='wlrm
https://staging.example.com/login&user=1+AND+1=(SELECT+1+FROM+PG_SLEEP(10))
https://staging.example.com/login&user=%23'%23\x22%0a-sleep(10)%23
https://staging.example.com/login&user=1';+WAITFOR+DELAY+'0code:10'--
https://staging.example.com/login&user=1%27%29+OR+SLEEP%280%29+AND+%28%27wlrm%27%3D%27wlrm
https://staging.example.com/login&user=SLEEP(10)/*'XOR(SLEEP(10))OR'|\x22XOR(SLEEP(10))OR\x22*/

Key Benefits of Threat Replay Testing

By implementing a TRT approach, you empower your organization with a robust, proactive security mechanism. Here’s how it adds value to your security strategy: 

• Actionable Insights: Detailed vulnerability reports help prioritize fixes and strengthen your API security posture.
• Real-world attack simulations: Use actual malicious requests to produce test cases, ensuring that your security measures remain relevant against active threats.
• Safe and controlled environment: Simulated test cases exclude harmful syntax and sensitive data (like authentication tokens), eliminating any risks of accidental system compromise.
• Augment Existing Testing Strategies: Dynamically explores attack variations and vectors, uncovering vulnerabilities missed by traditional static tools.

By implementing TRT, organizations can ensure they keep pace with rapidly evolving attackers and attack techniques. It is the future of API security, ensuring that real-world attack intelligence drives security improvements and facilitates a transformative shift from passive protection to active threat discovery. By embracing TRT, companies can turn attackers into valuable security assets, learning from their tactics and using their attacks to enhance their security posture.

Start Leveraging Threat Replay Testing

APIs are essential, dynamic, and critical to modern application infrastructure, but they also pose significant risks. Threat Replay Testing is a core innovation that transforms traditional security testing into adaptive, proactive defense mechanisms. With TRT, enterprises can stay ahead of attackers and ensure their APIs are secure, scalable, and resilient. 

At Wallarm, we deliver advanced unified API security solutions that are trusted by some of the world’s most innovative companies. From real-time protection to Threat Replay Testing, our platform offers an all-in-one approach to API security. Want to see how TRT can protect your APIs? Try Wallarm’s Threat Replay Testing today.