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Think like a hacker


By Jeff Feinman
February 15, 2009 — 
In the eyes of Mike Weider, the correct way of doing software security testing requires getting into the mind of the hacker.

The director of security products for IBM Rational said it takes a special breed of software professional to step into the driver’s seat of a hacker’s mentality and take the wheel. While quality assurance professionals can do security testing and smoke out some vulnerabilities, they usually have the customers’ thoughts in mind rather than those of the hacker.

“There is a need for this specialized security testing professional to anticipate how hackers think and use this slightly different way to test applications,” Weider said.

From a technology standpoint, there are two main approaches for testing software for security, and they are well known to developers and testers. One is exercising the software from what many call the outside-in approach: testing to see how the application responds to a simulated attack. The second is more of an inside-out approach, which looks for coding patterns that would highlight vulnerabilities in the code.

But security testing can be fundamentally a different ballgame than traditional testing because the emphasis is put on what an application should not do rather than what it should do. First, users don’t usually try to search out software bugs, while malicious attackers intentionally seek out vulnerabilities. When vulnerabilities are found by hackers, problems arise for other users instead of just a developer or group of developers.

Additionally, developers usually learn to avoid poor programming practices for their own projects, but it is difficult for security testers to keep up with the latest exploits because they grow every year. This makes it more difficult to ensure that secure programming practices are followed.

So what is the best way to carry out proper security testing? Vic DeMarines, vice president of products at security tool maker Vi Labs, shared Weider’s notion that testers need to think like the attackers themselves and to look for the easiest way to initiate a threat. Applications will have different levels of threats, depending on the nature of the application.

“If we’re talking about a financial application that’s running in a hosted environment, and it’s a Web application, the tester will be worried about someone trying to tamper with the logic,” DeMarines said. “If we’re talking about a piracy threat to a publisher, someone who is issuing software as part of their business, there are some ways you can go out and take a look at how those attacks are carried out, and then look at ways to bolster your defense against that. The first step is understanding how the attackers are going to look at the application and the methods they’re going to use to go after the vulnerabilities.”

Depending on what the threat is, organizations can either use their own resources or outsource for analysis to carry out this form of testing, DeMarines said. The ability to use an outside resource to test for threats depends on the amount of money an organization has.

Jacob West, manager of Fortify Software’s security research group, said the most important thing in assessing the security of software is to ask what can go wrong. That underpins any security testing activity because it puts the focus on things the software is not supposed to do instead of things it’s supposed to do.

“The challenges for security testers are going to be very similar to the challenges that developers went through as software security became a part of software development,” West said. “Early on, we had developers saying security isn’t their problem, that’s what the security team does, and slowly we’ve convinced programmers that security is part of the development process.

“The same evolution is going to happen in the security testing space. People who have thought of themselves as doing traditional quality assurance are going to have to think of security as part of their approach. As such, they’ll start to build up some knowledge of security and the kinds of things that can go wrong in specific circumstances.”

Gwyn Fisher, CTO of Klocwork, another security tool maker, said the whole issue with security is that a tester should not intend to find out if the software is secure at the end of the process. Instead, security testing must involve everyone; the architect should test his or her design assumptions for vulnerabilities, the coder should be responsible for testing what is being produced, and so forth.

“You get a secure product by following a secure development life cycle. You don’t get it by testing,” Fisher said. “It’s all about the notion of software security not coming from the outside in; it comes from the inside out.”

Adding security to the cycle
There is a great deal of talk in the software industry about making sure security is instilled throughout the software development life cycle, but there is no guarantee that such talk translates to action. However, Weider said IBM Rational has seen “an evolutionary approach,” where the security team looks to improve the security of the applications at the beginning of the development process.

“That works well to begin with, to have sort of a gatekeeper, but that also has the potential to become a bottleneck in that there’re very few security people, but there are hundreds or thousands of developers,” Weider said. “With the movement to agile approaches [that have] many smaller iterations, having that testing at the end of the process doesn’t make as much sense as having it embedded throughout the process.”

An agile process caters well to the idea of implementing security throughout the development life cycle because the concept calls for testing in each iteration, Weider explained. In the past, security testing has been something done last minute, and it was typical for testers to find a glaring vulnerability that would take weeks or a month to fix. The tester would then be left with the sticky situation of either delaying the release to fix the vulnerability, or looking the other way and letting the application go live with known bugs. Because of that, Weider said, there has been a push to integrate security testing into earlier phases of development.

One of the things IBM Rational is trying to do is to integrate security within development tools in such a way that it becomes a part of how an application is built, rather than something that’s bolted on after the software is developed.

Vi Labs' DeMarines agreed that security needs to be kept in mind throughout the development process. In terms of thinking about the next release as an application is under construction, a tester has the chance to figure out how to make it more resistant to tampering or piracy during the design phase. Testers can use tools that hackers might use to analyze or reverse-engineer an application. This can give the tester a better sense of how sturdy the application is.

“You don’t want to be starting to think about testing security as you’re coming into a release candidate,” DeMarines said. “You want to be looking at this fairly upfront when most of the functionality has been implemented in a way that you can test it, and then figure out how to make it resistant to the kinds of threats the enterprise is worried about.”

While there are many products on the market that allow software providers to scan source code for vulnerabilities, and it is important to do so, the key is acquiring the mentality to understand what the threat is and putting that feedback into the design, DeMarines added.

West said that mentality is pretty well ingrained in most developers today, and the enterprise software industry has realized that security needs to be a part of the full process. “There’s still a wide range of maturity levels in terms of how close companies are getting to obtaining that utopia of software being built in at every step, but for the most part, companies are doing whatever they’re able to now in order to make that a reality,” he said.

Positive vs. negative
When attempting to implement security throughout the development process, defining the proper security requirements is not always easy because they might be seen as redundant or difficult to comprehend for other professionals on a project. Some security requirements do come in the same form as traditional software requirements, specifying positive security features, such as a particular encryption algorithm the software should use, or making sure user accounts are disabled after three unsuccessful login attempts.

In security requirements, there is a much greater emphasis on negative requirements, where testing revolves around statements like, “Outside attackers should not be able to modify the contents of the Web page,” or, “Unauthorized users should not be able to access data.” This will have a big effect on how testing is carried out. Testing positive requirements involves creating conditions that will verify that the requirement is satisfied by the software. On the other hand, negative requirements can state that something should never occur, which would involve creating every possible set of conditions to determine that it won’t occur, which is close to impossible.

Most relevant requirements aren’t going to be positive, said West. Some will be redundant because they will tell the tester to avoid obvious vulnerabilities. A requirement like, “An attacker should never be able to take control of an application,” is the type of requirement that should be moved away from because it isn’t particularly useful. Good security requirements can give clues to testers downstream about what might constitute unintended behavior.

“You could say, for example, the application will never render un-encoded HTML or Javascript,” said Fortify's West. “That’s something a QA tester with relatively little security knowledge could go into a specific test case and verify. They can submit HTML characters to that page, and when it is displayed back to me, there shouldn’t be any shown. That’s going to be a challenge because there will always be a risk of turning a vulnerability around into a negative requirement that isn’t constructive for the downstream testers, because it's not verifiable in some way.”

West added that testers need to go to a lower level of granularity and turn vague requirements into smaller, more actionable ones. Testers should point out specific potential vulnerabilities, like stating that there is a possibility of a command injection vulnerability because shell scripts are running on the back end. In that case, the proper requirement might say, “No user input should be allowed to appear in a shell command that’s executed.”

IBM Rational’s Weider said that articulating security requirements can be difficult, and rarely are there people with the right skills to define what the requirements should be. He emphasized the importance of security in the design of applications, and said it is important to integrate threat modeling and other types of threat analysis into the design process to ensure that security is captured in the design and architecture.

Additionally, it’s not always easy to have all requirements accepted because there can be many more requirements than can fit into a given cycle, Weider said. This results in a “tug of war” as far as what requirements make it into the process. Because of this, testers need to prioritize security improvements to the application in the same way other software professionals prioritize quality and functional improvements.

“That is the challenge, but I think every year it’s getting a little better as security is becoming more accepted within development,” Weider said. “In the past, it wasn’t something that was well understood, but now as we’ve seen application security becoming one of the main vulnerabilities on the Internet as well as compliance issues, the priority of security in development requirements has been getting steadily better every year.”


Related Search Term(s): professional development, security, testing, IBM, Fortify, Klocwork, Vi Labs


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Comments

06/23/2009 10:30:01 AM EST

On a related note and for similar content, see our book "The Art of Software Security Testing" published in 2006 http://www.amazon.com/Art-Software-Security-Testing-Identifying/dp/0321304861/ref=ntt_at_ep_dpt_2, for example chapters 1, pg 11 "Think like an Attacker" and chapter 3 "The Secure Software Development Lifecycle"

United StatesElfriede Dustin


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