This post will discuss technical facets of RASP products, including how the technology works, how it integrates into an application environment, and the advantages or disadvantages of each. We will also spend some time on which application platforms supported are today, as this is one area where each provider is limited and working to expand, so it will impact your selection process. We will also consider a couple aspects of RASP technology which we expect to evolve over next couple years.


RASP works at the application layer, so each product needs to integrate with applications somehow. To monitor application requests and make sense of them, a RASP solution must have access to incoming calls. There are several methods for monitoring either application usage (calls) or execution (runtime), each deployed slightly differently, gathering a slightly different picture of how the application functions. Solutions are installed into the code production path, or monitor execution at runtime. To block and protect applications from malicious requests, a RASP solution must be inline.

  • Servlet Filters & Plugins: Some RASP platforms are implemented as web server plug-ins or Java Servlets, typically installed into either Apache Tomcat or Microsoft .NET to process inbound HTTP requests. Plugins filter requests before they reach application code, applying detection rules to each inbound request received. Requests that match known attack signatures are blocked. This is a relatively simple approach for retrofitting protection into the application environment, and can be effective at blocking malicious requests, but it doesn’t offer the in-depth application mapping possible with other types of integration.
  • Library/JVM Replacement: Some RASP products are installed by replacing the standard application libraries, JAR files, or even the Java Virtual Machine. This method basically hijacks calls to the underlying platform, whether library calls or the operating system. The RASP platform passively ‘sees’ application calls to supporting functions, applying rules as requests are intercepted. Under this model the RASP tool has a comprehensive view of application code paths and system calls, and can even learn state machine or sequence behaviors. The deeper analysis provides context, allowing for more granular detection rules.
  • Virtualization or Replication: This integration effectively creates a replica of an application, usually as either a virtualized container or a cloud instance, and instruments application behavior at runtime. By monitoring – and essentially learning – application code pathways, all dynamic or non-static code is mimicked in the cloud. Learning and detection take place in this copy. As with replacement, application paths, request structure, parameters, and I/O behaviors can be ‘learned’. Once learning is complete rules are applied to application requests, and malicious or malformed requests are blocked.

Language Support

The biggest divide between RASP providers today is their platform support. For each vendor we spoke with during our research, language support was a large part of their product roadmap. Most provide full support for Java; beyond that support is hit and miss. .NET support is increasingly common. Some vendors support Python, PHP, Node.js, and Ruby as well. If your application doesn’t run on Java you will need to discuss platform support with vendors. Within the next year or two we expect this issue to largely go away, but for now it is a key decision factor.

Deployment Models

Most RASP products are deployed as software, within an application software stack. These products work equally well on-premise and in cloud environments. Some solutions operate fully in a cloud replica of the application, as in the virtualization and replicated models mentioned above. Still others leverage a cloud component, essentially sending data from an application instance to a cloud service for request filtering. What generally doesn’t happen is dropping an appliance into a rack, or spinning up a virtual machine and re-routing network traffic.

Detection Rules

During our interviews with vendors it became clear that most are still focused on negative security: they detect known malicious behavior patterns. These vendors research and develop attack signatures for customers. Each signature explicitly describes one attack, such as SQL injection or a buffer overflow. For example most products include policies focused on the OWASP Top Ten critical web application vulnerabilities, commonly with multiple policies to detect variations of the top ten threat vectors. This makes their rules harder for attackers to evade. And many platforms include specific rules for various Common Vulnerabilities and Exposures, providing the RASP platform with signatures to block known exploits.

Active vs. Passive Learning

Most RASP platforms learn about the application they are protecting. In some cases this helps to refine detection rules, adapting generic rules to match specific application requests. In other cases this adds fraud detection capabilities, as the RASP learns to ‘understand’ application state or recognize an appropriate set of steps within the application. Understanding state is a prerequisite for detecting business logic attacks and multi-part transactions. Other RASP vendors are just starting to leverage a positive (whitelisting) security model. These RASP solutions learn how API calls are exercised or what certain lines of code should look like, and block unknown patterns.

To do more than filter known attacks, a RASP tool needs to build a baseline of application behaviors, reflecting the way an application is supposed to work. There are two approaches: passive and active learning. A passive approach builds a behavioral profile as users use the application. By monitoring application requests over time and cataloging each request, linking the progression of requests to understand valid sequences of events, and logging request parameters, a RASP system can recognizes normal usage. The other baselining approach is similar to what Dynamic Application Security Testing (DAST) platforms use: by crawling through all available code paths, the scope of application features can be mapped. By generating traffic to exercise new code as it is deployed, application code paths can be synthetically enumerated do produce a complete mapping predictably and more quickly.

Note that RASP’s positive security capabilities are nascent. We see threat intelligence and machine learning capabilities as a natural fit for RASP, but these capabilities have not yet fully arrived. Compared to competing platforms, they lack maturity and functionality. But RASP is still relatively new, and we expect the gaps to close over time. On the bright side, RASP addresses application security use cases which competitive technologies cannot.

We have done our best to provide a detailed look at RASP technology, both to help you understand how it works and to differentiate it from other security products which sound similar. If you have questions, or some aspect of this technology is confusing, please comment below, and we will work to address your questions. A wide variety of platforms – including cloud WAF, signal intelligence, attribute-based fraud detection, malware detection, and network oriented intelligence services – all market value propositions which overlap with RASP. But unless the product can work in the application layer, it’s not RASP.

Next we will discuss emerging use cases, and why firms are looking for alternatives to what they have today.