Moving Appsec To the Left

After spending the last year in a Product Security Architect role for a software company, I learned an important lesson:

Most application security efforts are misguided and ineffective.

While many security people have a good understanding of how to find application vulnerabilities and exploit them, they often don’t understand how software development teams work, especially in Agile/DevOps organizations. This leads to inefficiencies and a flawed program. If you really want to build secure applications, you have to meet developers where they are, by understanding how to embed security into their processes.

In some very mature Agile organizations, application security teams have started adding automated validation and testing points into their DevOps pipelines as DevSecOps (or SecDevOps, there seems to be a religious war over the proper terminology) to enforce the release of secure code. This is a huge improvement, because it ensures that you can eliminate the manual “gates” that block rapid deployment. My personal experience with this model is that it’s a work-in-progress, but a necessary aspirational goal for any application security program. Ultimately, if you can’t integrate your security testing into a CI/CD pipeline, the development process will circumvent security validation and introduce software vulnerabilities into your applications.

However, this is only one part of the effort. In Agile software development, there’s an expression, “shifting to the left,” which means moving validation to earlier parts of the development process.  While I could explain this in detail, already has an excellent post on the topic. In my role, I partnered with development teams by acting as a product manager and treating security as a customer feature, because this seemed more effective than the typical tactic of adding a bunch of non-functional requirements into a product backlog.

A common question I would receive from scrum teams is whether a security requirement should be written as a user story or simply as acceptance criteria. The short answer is, “it depends.” If the requirement translates into direct functional requirements for a user, i.e. for a public service, it is better suited as a user story with its own acceptance criteria. If the requirement is concerned with a back-end service or feature, this is better expressed as acceptance criteria in existing stories. One technique I found useful was to create a set of user security stories derived from the OWASP Application Security Verification Standard (ASVS) version 3.0.1 that could be used as a template to populate backlogs and referenced during sprint planning. I’m not talking about “evil user stories,” because I don’t find those particularly useful when working with a group of developers.

Another area where product teams struggle is whether a release should have a dedicated sprint for security or add the requirements as acceptance criteria to user stories throughout the release cycle. I recommend having a security sprint for all new or major releases due to the inclusion of time-intensive tasks such as manual penetration testing, architectural risk assessments and threat modeling. But this should be a collaborative process with a product team and  I met regularly with product owners to assist with sprint planning and backlog grooming. I also found it useful to add a security topic to the MVS (minimum viable solution) contract.

I don’t pretend to have all the answers when it comes to improving software security, but spending time in the trenches with product development teams was an enlightening experience. The biggest takeaway: security teams have to grok the DevOps principle of collaboration if we want more secure software. To further this aim, I’m posting the set of user security stories and acceptance criteria I created here. Hopefully, it will be the starting point for a useful dialogue with your own development teams.

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