PCI – Going Beyond the Standard: Part 17, Vulnerability Scanning & Penetration Testing

Far too often, security is seen as a project, especially if PCI compliance is the goal. The requirements for vulnerability scanning and penetration testing are therefore seen as just another tick-in-a-box and their significant benefits lost.

External vulnerability scanning is the only requirement which must be outsourced and run by an approved scanning vendor (ASV, list here), the other requirements; internal vulnerability scanning, external penetration testing and internal penetration testing can by run by internal resources IF, and ONLY if, you can adequately demonstrate the requisite skill-sets in-house.

Of course, in order to save money, it is very tempting to skate by on the bare minimum, and unfortunately some security vendors (including QSAs) will allow you to do just that. Which is a shame, almost to the point of being irresponsible, as no other requirements give you a truer indication of your actual security posture than these.

Think of it this way; the bad guys use the EXACT same techniques to break into your systems that the good guys use to tell you what’s wrong. The ONLY differences between a hacker and an ethical hacker are intent and moral code, the skill-sets and mind-sets are the same.

Between vulnerability scanning and penetration testing, you have roughly 50% of your vulnerability management program sown up. Patch management management, risk management etc. make up the rest. However, the trick that’s almost always done poorly – if at all – is the integration of vulnerability management with asset management and change control. Any change to your environment should have appropriate vulnerability management processes around them, from a quick directed scan to a full blown credentialed penetration test, and all should be in-line with agreed configuration standards (as defined against each asset).

Going above and beyond PCI in scanning and pen. testing is relatively simple, but it’s not cheap in terms of resource cost. It also demands a maturity of process and a significant shift in culture to accept the ‘overhead’, but it’s more than worth it:

1. External Vulnerability Scanning – No choice but to use an ASV, but you should choose a vendor that provides 2 things at either no, or little, extra cost; Monthly scans (PCI requires quarterly), and unlimited directed scans (against single IPs, or subnets). Performed correctly, monthly scans and directed scans initiated by change control processes go significantly above and beyond. Note: For PCI do NOT open your external firewall/routing devices to your ASV’s IP addresses. Why would you decrease your security posture to test your security posture? Just run one scan for PCI, and THEN open your firewalls so that scanners can do a more thorough job. Keep these profiles separate, one for PCI only, one for your entire business.

2. Internal Vulnerability Scanning – You can do this yourself, and I’ve lost count of the number of clients running basic installations of Nessus, but unless you have significant expertise in how to configure it AND understand the results, don’t do it. For a start, any good QSA will fail you for lack of expertise, but do you really have the time to keep it up to date? Again, running internal scans monthly and as directed by change control goes above and beyond. Having two scan profiles is also a nice feature, but if the scan engine is capable of doing more than just rattle the windows (in the ubiquitous house analogy) and can actually perform a deeper scan / reconnaissance, then you have knocked this one out the park. PCI compliance is never security, do internal scanning as far above PCI minimums as you can afford.

3. External Penetration Testing – PCI requires that you attempt to break in (without breaking) via your Internet-facing presence, but poor guidance on what the test should consist of, combined with an enormous price-compression of pen. testing services means that this effort is usually more automated than I would consider appropriate. A pen. test is supposed to be a person with the necessary skills trying for days on end to discover ways into your systems. This is rarely the case now, but is EXACTLY what your should be doing. The Internet is where most breaches originate (used to be internal), so having a VERY robust security posture from the-outside-in is of paramount importance. Do NOT skimp on this one.

PCI calls for annual pen. tests, and to go above and beyond you need to perform these more frequently. This should not be an enormous cost, and most pen. test vendors can provide an infinitely scalable service based on scope and call-off days.

4. Internal Penetration Testing – Same premise as the external pen. test, but this time from the inside. PCI requires that this test simulate an attacker ‘plugging in’ where the admins sit and seeing what they can do from scratch. Above and beyond is therefore very simple; give the pen. tester FULL access to the environment, as well as credentials to go even further where appropriate. Like scanning, you have one test for PCI, then another test for your business.

There will be times when a simple vuln. scan of a system that has undergone change is not sufficient, so having a directed pen. test process available for critical business changes is very important.

None of the above processes should be stand-alone concepts, and should be very tightly integrated with risk assessment, change control and asset management processes to be truly effective. Vulnerability Management represents the end to each cycle of your security program (Plan > Do > Check > Act > Repeat), and ensures that your security posture always remain in-line with your business goals.

It bears repeating, do NOT skimp on this requirement, you will pay far more when you have to clean up the mess after a breach.

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