Skip to main content

Black Box versus White Box testing and when to use them

I have recently been speaking to many security professionals and asking them about black box and white box testing. I have used it as an interview question on many occasions as well. People's answers are varied and interesting, but I thought I would share my views briefly here.

Firstly, what are black box testing and white box testing, or grey box testing for that matter? Simply put, a black box test is one where the tester has no knowledge of the internal structure or workings of the system and will usually test with security protections in place. They may not even be given credentials to a system that requires authentication. This would be equivalent to what a hacker would have access to.

The opposite extreme is a white box test, where the tester has full knowledge of the system and access to the code, system settings and credentials for every role, including the administrator. The tester will likely be testing from inside the security perimeter. Grey box testing sits somewhere in the middle, where the tester will have knowledge of the functionality of the system and the overall components, but not detailed knowledge. They will usually have credentials, but may still test with some security controls in place.

So, when would you use the different levels of testing? Personally, I think that grey box testing is neither one thing nor the other and holds little value. For me, the motivation behind black box testing is compliance, whereas the motivation behind white box testing is security. With a white box test you are far more likely to find security issues, understand them and be able to fix or mitigate them effectively, so why wouldn't you do it? The black box test is supposedly what a hacker would see, but they have far more time, so it isn't even representative. The only reason to perform a black box test is to pass some audit that you are afraid you might fail if you perform a full white box test, in my opinion.

If you actually want to be secure, then make sure you always commission white box tests from your security testers.

Comments

Popular Posts

Trusteer or no trust 'ere...

...that is the question. Well, I've had more of a look into Trusteer's Rapport, and it seems that my fears were justified. There are many security professionals out there who are claiming that this is 'snake oil' - marketing hype for something that isn't possible. Trusteer's Rapport gives security 'guaranteed' even if your machine is infected with malware according to their marketing department. Now any security professional worth his salt will tell you that this is rubbish and you should run a mile from claims like this. Anyway, I will try to address a few questions I raised in my last post about this. Firstly, I was correct in my assumption that Rapport requires a list of the servers that you wish to communicate with; it contacts a secure DNS server, which has a list already in it. This is how it switches from a phishing site to the legitimate site silently in the background. I have yet to fully investigate the security of this DNS, however, as most

Security Through Obscurity

I have been reminded recently, while looking at several products, that people still rely on the principle of 'security through obscurity.' This is the belief that your system/software/whatever is secure because potential hackers don't know it's there/how it works/etc. Although popular, this is a false belief. There are two aspects to this, the first is the SME who thinks that they're not a target for attack and nobody knows about their machines, so they're safe. This is forgivable if misguided and false. See my post about logging attack attempts on a home broadband connection with no advertised services or machines. The second set of people is far less forgivable, and those are the security vendors. History has shown that open systems and standards have a far better chance of being secure in the long run. No one person can think of every possible attack on a system and therefore they can't secure a system alone. That is why we have RFCs to arrive at ope

Web Hosting Security Policy & Guidelines

I have seen so many websites hosted and developed insecurely that I have often thought I should write a guide of sorts for those wanting to commission a new website. Now I have have actually been asked to develop a web hosting security policy and a set of guidelines to give to project managers for dissemination to developers and hosting providers. So, I thought I would share some of my advice here. Before I do, though, I have to answer why we need this policy in the first place? There are many types of attack on websites, but these can be broadly categorised as follows: Denial of Service (DoS), Defacement and Data Breaches/Information Stealing. Data breaches and defacements hurt businesses' reputations and customer confidence as well as having direct financial impacts. But surely any hosting provider or solution developer will have these standards in place, yes? Well, in my experience the answer is no. It is true that they are mostly common sense and most providers will conform