Tuesday, November 17, 2015

Panel Selection of Penetration Testing Vendors

Most large companies have settled into a repeatable model in the way they undertake penetration testing and engage with their penetration testing suppliers. A popular model for companies that need to have several dozen pentests performed per year is to have a “board” or “panel” of three or four vetted companies and to rotate one provider in and out of the scheme per year – meaning that there is potentially a total refresh of providers every few years.

As vendor performance models go there is a certain undeniable logic to the process. However, it is worth questioning if these “board” models actually deliver better results – in particular, are the full spectrum of vulnerabilities being examined and are the individual consultants capable of delivering the work? In general, I’d argue that such a model often fails to meet these core requirements.

Advanced companies (e.g. brand-name software manufacturers) that require access to the most skilled talent-pool of penetration testers and reverse engineers tend to select vendors based upon the skills and experience of the consultants they employ – often specifically calling out individual consultants by names within the terms of the contract. They also pay premium rates to have access to that exclusive talent pool. In turn, the vendors that employ those consultants market and position their own companies as advanced service providers. For these companies, talent is the critical buying decision and it is not uncommon for the client organization to engage with new vendors when highly skilled or specialized consultants move between service providers.

Most large companies are not as sophisticated in discerning the talent pool needed to review and secure their products – yet still have many of the same demands and needs from a penetration testing skills perspective. For them, vendor selection is often about the responsiveness of the service provider (e.g. can they have 6 penetration testers onsite within two weeks in Germany or Boston) and the negotiated hourly-rate for their services. The churn of vendors through the “board” model is typically a compromise effort as they try to balance the needs of negotiating more favorable contractual terms, overcoming a perception of skill gaps within their providers consulting pool, and serve a mechanism for tapping a larger pool of vetted consultants.

From past observations, there are several flaws to this model (although several elements are not unique to the model).
  1. Today's automated vulnerability scanners (for infrastructure, web application, and code review) are capable of detecting up to 90% of the vulnerabilities an “average” penetration tester can uncover manually if they use their own scripts and tools. Managed vulnerability scanning services (e.g. delivered by managed security service providers (MSSP)) typically reach the same 90% level, but tend to provide the additional value of removing false positives and confirming true positives. If these automated tools and services already cover 90% of the vulnerability spectrum, organizations need to determine whether closing the gap on the remaining 10% is worth the consulting effort and price. Most often, the answer is “yes, but…” where the “but…” piece is assigned a discrete window of time and effort to uncover or solve – and hence value. Organizations who adopt the “board” approach often fail to get the balance between tools, MSSP, and consultant-led vulnerability discovery programs. There are significant cost savings to be had when the right balances have been struck.
  2. Very few consultants share the same depth of skills and experience. If an organization is seeking to uncover vulnerabilities that lie out of reach of automated discovery tools, it is absolutely critical that the consultant(s) undertaking the work have the necessary skills and experience. There is little point throwing a 15 year veteran of Windows OS security at an Android mobile application served from the AWS cloud – and vice versa. To this end, clients must evaluate the skill sets of the consultants that are being offered up by the vendor and who are expected to do the work. The reality of the situation is that clients that don’t pay the necessary attention can almost guarantee that they’ll get the second-rung consultants (pending availability) to perform this important work. The exception being when a new vendor is being evaluated, and they’ll often try to throw their best at the engagement for a period of time in order to show their corporate value – but clients should not anticipate the same level of results in subsequent engagements unless they are specific about the consultants they need on the job.
  3. Rotating a vendor in or out of a program based upon an annual schedule independent of evaluating the consultants employed by the company makes little sense. Many penetration testing companies will have a high churn of technical staff to begin with and their overall technical delivery capabilities and depth of skills specialization will flux though-out the year. By understanding what skill sets the client organization needs and the amount of experience in each skill area in advance, those organizations can better rationalize their service providers consulting capabilities – and negotiate better terms.
  4. Because consultant skills and experience play such an important role in being able to uncover new vulnerabilities, client organizations should consider cross-vendor teams when seeking to penetration test and secure higher-priority infrastructure, applications, and products. Cherry-picking named consultants from multiple vendors to work on an important security requirement tends to yield the best and most comprehensive findings. Often there is the added advantage of those vendors choosing to compete to ensure that their consultants do the best team work on the joint project – hoping that more follow-on business will fall in their direction.

While “board” or “panel” approaches to penetration testing vendor management may have an appeal from a convenience perspective, the key to getting the best results (both economical and vulnerability discovery) lies with the consultants themselves. 

Treating the vendor companies as convenient payment shells for the consultants you want or need working on your security assignments is OK as long as you evaluate the consultants they employ and are specific on which consultants you want working to secure your infrastructure, applications, and products. To do otherwise is a disservice to your organization.

-- Gunter

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