Pragmatic WAF Management: The Trouble with WAFBy Adrian Lane
We kicked off the Pragmatic WAF series by setting the stage in the last post, highlighting the quandary WAFs represent to most enterprises. On one hand, compliance mandates have made WAF the path of least resistance for application security. Plenty of folks have devoted a ton of effort to making WAF work, and they are now looking for even more value, above and beyond the compliance checkbox.
On the other hand, there is general dissatisfaction with the technology, even from folks who use WAFs extensively. Before we get into an operational process for getting the most out of your WAF investment, it’s important to understand why security folks often view WAF with a jaundiced eye. The opposing viewpoints between security, app developers, operations, and business managers help pinpoint the issues with WAF deployments. These issues must be addressed before the technology can reach the adoption level of other security technologies (such as firewalls and IPS). The main arguments against WAF are:
- Pen-tester Abuse: Pen testers don’t like WAFs. There is no reason to beat around the bush. First, the technology makes a pen tester’s job more difficult because a WAF blocks (or should block) the kind of tactics they use to attack clients via their applications. That forces them to find their way around the WAF, which they usually manage. They are able to reach the customer’s environment despite the WAF, so the WAF must suck, right? More often the WAF is not set up to block or conceal the information pen testers are looking for. Information about the site, details about the application, configuration data, and even details on the WAF itself leak out, and are put to good use by pen testers. Far too many WAF deployments are just about getting that compliance checkbox – not stopping hackers or pen testers. So the conclusion is that the technology sucks – rather than pointing at the implementation.
- WAFs Breaks Apps: The security policies – essentially the rules that tell what a WAF should either block or allow to pass through to the application – can (and do) block legitimate traffic at times. Web application developers are used to turning code – basically pushing changes and new functionality to web applications several times per week, if not more often. Unless the ‘whitelist’ of approved application requests gets updated with every application change, the WAF will break the app, blocking legitimate requests. The developers get blamed, they point at operations, and nobody is happy.
- Compliance, Not Security: A favorite refrain of many security professionals is, “You can be compliant and still not be secure.” At least the ones who know what they’re talking about. Regulatory and industry compliance initiatives are desgined to “raise a very low bar” on security controls, but compliance mandates inevitably leave loopholes – particularly in light of how often they can realistically be updated. Loopholes attackers can exploit. Even worse, the goal of many security programs become to pass compliance audits – not to actually protect critical corporate data. The perception of WAF as a quick fix for achieving PCI-DSS compliance – often at the expense of security – leaves many security personnel with a negative impression of the technology. WAF is not a ‘set-and-forget’ product, but for compliance it is often used that way – resulting in mediocre protection. Until WAF proves its usefulness in blocking real threats or slowing down attackers, many remain unconvinced of WAF’s overall value.
- Skills Gaps: Application security is a non-trivial endeavor. Understanding spoofing, fraud, non-repudiation, denial of service attacks, and application misuse are skills rarely all possessed by any one individual. But all those skills are needed by an effective WAF administrator. We once heard of a WAF admin who ran the WAF in learning mode while a pen test was underway – so the WAF thought bad behavior was legitimate! Far too many folks get dumped into the deep waters of trying to make a WAF work, without a fundamental understanding of the application stack, business process, or security controls. The end result is that rules running on the WAF miss something – perhaps not accounting for current security threats, not adapted to changes in the environment, or not reflecting the current state of the application. All too often, the platform lacks adequate granularity to detect all variants of a particular threat, or essential details are not coded into policies, leaving an opening to be exploited. But is this an indictment of the technology, or how it is utilized?
- Perception and Reality: Like all security products, WAFs have undergone steady evolution over the last 10 years. But their perception is still suffering because original WAFs were themselves subject to many of the attacks they were supposed to defend against (WAF management is through a web application, after all). Early devices also had high false positive rates and ham-fisted threat detection at best. Some WAFs bogged down under the weight of additional policies, and no one ever wanted to remove policies for fear of allowing an attacker to compromise the site. We know there were serious growing pains with WAF, but most of the current products are mature, full-featured, and reliable – despite persistent perception.
But when you look at these complaints critically, much of the dissatisfaction with WAFs comes down to poor operational management.
Our research shows that WAF failures are far more often a result of operational failure than of fundamental product failure. Make no mistake – WAFs are not a silver bullet – but a correctly deployed WAF makes it much harder to attack the app or to completely avoid detection. The effectiveness of WAF is directly related to the quality of people and processes used to keep it current. The most serious problems with WAF are not about technology, but with management.
So that’s what we will present. A pragmatic process to manage Web Application Firewalls, in a way that overcomes the management and perception issues which plague this technology. As usual we will start at a high level, describing the entire process, and then drill down into each aspect.