Vulnerabilities / Threats
6/5/2013
11:27 PM
Vincent Liu
Vincent Liu
Commentary
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What To Ask Your Penetration Tester

The importance of manual pen testing

Third installment in a series on spotting a novice pen tester

Reviewing the results of a penetration test and discussing methodology is another way to assess the skill level of your pen tester (and the overall quality of the penetration test). What this means is that by asking a few simple questions and evaluating the quality of his or her responses, you can get a good read of his or her abilities. It doesn't mean that if a pen tester fails to break into your system that he or she is a novice. Even the best testers run into targets that are secure.

So start by asking about methodology. What did they do during the penetration test? Zero in on manual testing and how they approached that type of testing. Ask specific questions about what they did for certain exposed services and vulnerability classes. A novice tester is usually highly reliant on the tool for findings, so their answers will usually circle back to the tool. As a general rule, automated tools should make up at most 20 percent (and, in extreme cases, 25 percent) of the time spent during a penetration test. Ask about how a tool was used, but focus more on how they followed-up with manual testing.

When quizzing your pen tester, be sure to differentiate between the act of validating tool results and manual penetration testing. The two are commonly (and mistakenly) used interchangeably.

What you want to know is what types of manual testing were performed beyond eliminating false positives from the report. You really want to know if they attempted to exploit any of the identified issues, which would indicate that they know more than just validation. Conversely, if you find that your reports contain several false positives, there's a good chance that your pen tester doesn't even have the ability to perform the most basic manual validation, so it's very unlikely that he or she was able to perform any manual pen testing.

Don't Fear The Questions
In the population of penetration testers, there exists very skilled and talented assessors, but there also exists an ever greater number of simple tool jockeys who have applied the name of "pen tester" to themselves despite lacking the skill. Then, as the number of unqualified "pen testers" continues to multiply, it becomes all the more important to understand the different levels of pen testers and how to identify them.

Until then, don't be shy about questioning your testers about their results and methodology. They should be clear and open about what they did; if they aren't, then I would recommend reconsidering your choice of assessor.

A hallmark of a better pen tester is the ability to locate and then exploit any identified vulnerabilities. In order to properly and successfully exploit issues, a tester must have a strong understanding of how the vulnerability is manifested, how the environment affects that instance, and how to adapt an attack to properly take advantage of the weakness. The ability to exploit and adapt to each environment is a characteristic of an advanced penetration tester, whose qualities we'll explore in our next installment.

Vincent Liu (CISSP) is a Managing Partner at Stach & Liu, a security consulting firm providing services to the Fortune 500, global financial institutions, and high-tech startups. In this role, he oversees firm strategy, practice development, and client matters. Vincent is ... View Full Bio

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