Dark Reading is part of the Informa Tech Division of Informa PLC

This site is operated by a business or businesses owned by Informa PLC and all copyright resides with them.Informa PLC's registered office is 5 Howick Place, London SW1P 1WG. Registered in England and Wales. Number 8860726.

Perimeter

6/15/2011
01:47 PM
John H. Sawyer
John H. Sawyer
Commentary
50%
50%

WAFs Have Benefits, But Are Not A Security Cure-all

WAFs can provide a good layer of defense against attacks, but they can't solve all Web app-sec problems the way vendors would like you to think

Web application firewalls (WAF) are becoming more common in organizations of all sizes, thanks to PCI regulations requiring the use of WAFs or regular Web application security assessments. Many organizations are choosing to go with the one-time cost and annual maintenance fees associated with a WAF solution because it is always on. Economically, the decision makes sense since a Web app assessment is only a snapshot in time compared to a WAF, but WAFs cannot understand the complexities of an application's logic as a human being who is testing the application.

The problem is that outrageous claims are often found in WAF vendors' marketing materials that make buyers think a WAF is the silver bullet to preventing Web application compromises. I've seen examples that include how one WAF can stop all common application vulnerabilities, and that implementing a WAF is an adequate substitution for a thorough code review. Of course, what they don't tell you is just how much they can't detect.

A recent conversation among friends centered on a security breach at a security vendor that, ironically, just happens to also produce a commercial WAF. Public details stated the breach was through a website that ultimately led to the exposure of customer data. As if on cue, one friend mentioned that WAFs are never a permanent solution, which prompted another friend to ask, "What is?" My response? Three words: Fix the vulnerabilities.

Of course, that wasn't what he was looking for. He wanted a more detailed answer, so I unleashed one, and what I wanted to convey through my answer was that my "fix the vulns" wasn't a quick, generic security consultant answer. Instead, it was based on years of front-line experience securing a large environment and fighting the proliferation of poorly coded Web apps.

The tiresome phrase "there is no silver bullet for security" has become old and boring, but it still holds true to this discussion. (Yes, I know. I used it above.) As much as the marketing folks will try and convince you that their WAFs will protect your vulnerability-riddled Web app, there's no way that a WAF can understand all of your app's logic. Because, when they say that it protects against all common vulnerabilities, do they mean logic flaws, too? I doubt it.

Personally, I'm pretty sure logic flaws fall within the common category. The problem is they are often missed because automated scanners cannot detect them easily like the more well-known vulnerabilities, such as cross-site scripting and SQL injection. Similarly, a WAF will miss them because it's not possible to write a regular expression to catch a logic flaw.

So what's a SMB to do to protect its Web applications? Well, for one, fix the vulnerabilities! I say that partially in jest, but it's important to emphasize the need for developers to follow secure coding practices and have that code reviewed for vulnerabilities. My good friend, Kevin Johnson, recently gave a webcast for SANS called "Ninja Developers: Penetration Testing and Your SDLC." In the webcast, Kevin provides good advice on how developers can perform basic penetration techniques during development using tools like w3af to help find flaws before they make it to production.

Unfortunately, vulnerabilities will still make it through QA, and that's where the good, ol' defense-in-depth approach becomes key in helping defend against and detect attacks. A WAF can provide basic protection against "common" attacks and also act as an intrusion detection system (IDS). Log monitoring provides a layer critical for detecting and responding to anomalies that could indicate a successful attack. And don't forget that the underlying Web service and operating system needs to be patched as soon as patches become available.

I still stand by my statement -- fix the vulnerabilities -- but that does not in any way nullify the fact that best practices, like those just mentioned, should be followed. Just as it is impossible for a WAF to protect against all vulnerabilities a Web application might suffer, it's difficult for a penetration tester to find all vulnerabilities.

John Sawyer is a Senior Security Analyst with InGuardians. The views and opinions expressed in this blog are his own and do not represent the views and opinions of his employer. He can be reached at [email protected]

Comment  | 
Print  | 
More Insights
Comments
Newest First  |  Oldest First  |  Threaded View
COVID-19: Latest Security News & Commentary
Dark Reading Staff 9/21/2020
Hacking Yourself: Marie Moe and Pacemaker Security
Gary McGraw Ph.D., Co-founder Berryville Institute of Machine Learning,  9/21/2020
Startup Aims to Map and Track All the IT and Security Things
Kelly Jackson Higgins, Executive Editor at Dark Reading,  9/22/2020
Register for Dark Reading Newsletters
White Papers
Video
Cartoon
Current Issue
Special Report: Computing's New Normal
This special report examines how IT security organizations have adapted to the "new normal" of computing and what the long-term effects will be. Read it and get a unique set of perspectives on issues ranging from new threats & vulnerabilities as a result of remote working to how enterprise security strategy will be affected long term.
Flash Poll
How IT Security Organizations are Attacking the Cybersecurity Problem
How IT Security Organizations are Attacking the Cybersecurity Problem
The COVID-19 pandemic turned the world -- and enterprise computing -- on end. Here's a look at how cybersecurity teams are retrenching their defense strategies, rebuilding their teams, and selecting new technologies to stop the oncoming rise of online attacks.
Twitter Feed
Dark Reading - Bug Report
Bug Report
Enterprise Vulnerabilities
From DHS/US-CERT's National Vulnerability Database
CVE-2020-25596
PUBLISHED: 2020-09-23
An issue was discovered in Xen through 4.14.x. x86 PV guest kernels can experience denial of service via SYSENTER. The SYSENTER instruction leaves various state sanitization activities to software. One of Xen's sanitization paths injects a #GP fault, and incorrectly delivers it twice to the guest. T...
CVE-2020-25597
PUBLISHED: 2020-09-23
An issue was discovered in Xen through 4.14.x. There is mishandling of the constraint that once-valid event channels may not turn invalid. Logic in the handling of event channel operations in Xen assumes that an event channel, once valid, will not become invalid over the life time of a guest. Howeve...
CVE-2020-25598
PUBLISHED: 2020-09-23
An issue was discovered in Xen 4.14.x. There is a missing unlock in the XENMEM_acquire_resource error path. The RCU (Read, Copy, Update) mechanism is a synchronisation primitive. A buggy error path in the XENMEM_acquire_resource exits without releasing an RCU reference, which is conceptually similar...
CVE-2020-25599
PUBLISHED: 2020-09-23
An issue was discovered in Xen through 4.14.x. There are evtchn_reset() race conditions. Uses of EVTCHNOP_reset (potentially by a guest on itself) or XEN_DOMCTL_soft_reset (by itself covered by XSA-77) can lead to the violation of various internal assumptions. This may lead to out of bounds memory a...
CVE-2020-25600
PUBLISHED: 2020-09-23
An issue was discovered in Xen through 4.14.x. Out of bounds event channels are available to 32-bit x86 domains. The so called 2-level event channel model imposes different limits on the number of usable event channels for 32-bit x86 domains vs 64-bit or Arm (either bitness) ones. 32-bit x86 domains...