Many times, in the course of our work as analysts (SOC, DFIR, etc.), we run tools…and that’s it. But do we often stop to think about why we’re running that tool, as opposed to some other tool? Is it because that’s the tool everyone we know uses, and we just never thought to ask about another? Not so much the how, but do we really think about the why?
The big question, however, is…do we validate our tools? Do we verify that the tools are doing what they are supposed to, what they should be doing, or do we simply accept the output of the tool without question or critical thought? Do we validate our tools against our investigative goals?
Back when Chris Pogue and I were working PCI cases as part of the IBM ISS X-Force ERS team, we ran across an instance where we really had to dig in and verify our toolset. Because we were a larger team, with varying skill levels, we developed a process for all of the required searches, scans and checks (search for credit card numbers, scans for file names, paths, hashes, etc.) based on Guidance Software’s EnCase product, which was in common usage across the team. As part of the searches for credit card numbers (CCNs), we were using the built-in function isValidCreditCard(). Not long after establishing this process, we had a case where JCB and Discover credit cards had been used, but these weren’t popping up in our searches.
Chris and I decided to take a look at this issue, and we went to the brands and got test card numbers…card numbers that would pass the necessary checks (BIN, length, Luhn check), but were not actual cards used by consumers. We ran test after test, and none using the isValidCreditCard() returned the card numbers. We tried reaching out via the user portal, and didn’t get much in the way of a response that was useful. Eventually, we determined that those two card brands were simply not considered “valid” by the built-in function, so we overrode that function with one of our one, one that included 7 regexes in order to find all valid credit card numbers, which we verified with some help from a friend.
We learned a hard lesson from this exercise, one that really cemented the adage, “verify your tools”. If you’re seeing
[…]
Content was cut in order to protect the source.Please visit the source for the rest of the article.
[…]
Content was cut in order to protect the source.Please visit the source for the rest of the article.
This article has been indexed from Windows Incident Response
Read the original article: