Monthly Archives: May 2009

WAFing it up

I should disclose up front that I derive my living today supporting WAF technologies for a large corporation, and so it will come as no surprise that I have a few opinions on the use of WAF technology and in general how to go about protecting web applications.

If you’re a purist and feel adamantly for or against Web Application Firewalls, I would urge you to consider the roots of defense-in-depth – just like the spoon in The Matrix, there is no silver bullet. OWASP‘s concepts are as close as we’ll ever get to that silver bullet.

Secure Coding won’t get you out of every vulnerability and neither will a WAF, if for no other reason than the sheer complexity of the equipment needed to stand up web-enabled services introduces too many interdependencies to think every coder, developer, and vendor got everything right and there will never be a problem. — If you disagree with that, put down the Vendor Kool-Aid now before it’s too late.

Positive / Negative Security Models
Good grief.  Techie speak if ever there was any. Reminds me of the James Garner movie Tank, where little Billy is exposed to negative feedback in order to arrest his “bad” behavior. In my house, that’s called a spanking and you get one when it’s appropriate. My kids know what a spanking is and so does anyone reading this thread. Without googling, name two WAF products based on each of these Security Models: Positive & Negative — It’s okay, I’ll wait for you.

And we’re back…
On the topic of Security Models, I tend to think it takes a combination of protective technologies to provide any actual risk/threat  mitigation. I would personally like to see developers take advantage of a WAF’s ability to see how an application behaves. Moste developers don’t think of in terms of which web page does what, instead they’re working with APIs and objects. This is unfortunate because the rest of the world sees these applications as URL’s. The WAF can be that bridge to the developers. A WAF could in theory help the developer ensure that a specific sequence of events happens before a transaction is processed or prompt the client before transactions occur in specific instances to avoid CRSF.

To bring things back around to my original point. I do agree that the more complex a web application is and the more servers required to make a service available online, the more vulnerable and difficult to secure that application or service will be. I’m not sure who’s law that is but I’m sure one exists, complexity breeds more complexity.

No surprise there, if you are protecting a complex asset then it will be high maintenance — I said to put down the Kool-Aid, it’s for you own good – nothing is free!

Network Zoning – Be the Zone

A while back I started a series on Network Zoning and like most procrastinating, over-achievers: I got side-tracked (is that a self-induced form of ADD?) ! I have had the pleasure of interacting with a number of folks on the zoning topic, and so I wanted to take a moment to tack on an additional concept that doesn’t always get much attention but is very relevant in your network zoning design.

PERSPECTIVE and the impact of perspective.

Perspective in Network Zoning is a little like determine the perspective of an email without knowing the sender. If you’ve ever sent a witty email to someone who didn’t share your sense of humor, you’ve been impacted by perspective. Please be careful not to confuse perspective with context. Perspective deals with a vantage point, while a context is the surrounding details.

When zoning, the perspective of the actual components, users, and threats dictates a given device’s zoning requirements. Theoretically perspective actually defines the security posture.

Did that hurt? Just a little?

Sample Four-Zone Network

The configuration for each of these devices in this illustration is relative to their location in the network. Their perspective determines their configuration. Obvious right? Please keep in mind, the External Firewall or Internal Firewall could easily be a router with ACL’s

Consider that the External Firewall in this illustration sees untrusted incoming traffic and passes only traffic based on rules for the more-trusted networks.

This “trusted” traffic of the External Firewall is actually UNTRUSTED TRAFFIC for the Internal Firewall! After all this is the UNTRUSTED interface on the Internal Firewall.

The Internal firewall can be configured with the same blocking rules of the External Firewall in addition to new rules that are applicable to protecting the Internal Networks.

The addition or the difference in security configuration for internal or external firewalls will be controlled in-part due to perspective because you could obviously implement the same overall security policy on both firewalls but the expectation for what threats exist where will be based on perspective.

In the same light, your zones will have traffic or usage patterns and requirements relative to their placement in the network. External DNS servers will be configured and protected differently than Internal DNS servers. Network resources talking across zones will work differently than talking inside a zone. Your security practices and configuration will change accordingly. The configuration for a given zone will be driven by perspective – requirements will map out differently based on the perspective of users, threats, and policies.

Perspective will show up within the logs as well. When you review the logs on your devices, you will react differently to external threats to your internal servers logged on the actual internal server versus the External Firewall.

When you build out your network zone, be sure to keep perspective in mind. You may choose to overlap policies as a defense in depth practice, but please take care to define your zoning appropriately.

What’s your perspective?
Drop me a line and let me know!

Off to the WAF races

PCI DSS called for implementation of code reviews and web-application firewalls (WAF’s) in order to continue compliance and fight off the Breach Boogieman. Organizations can also conduct code reviews, as outlined in section 6.

Some ‘experts’ believe the web firewalls are just another piece of technology being thrown on the bonfire, while others believe you will never find all the potential bugs and flaws in an organization’s custom code, let-alone commercial software.

Interestingly, there continue to be heated discussions debating the usefulness of WAF’s, where they have to be deployed, what they are supposed to inspect, and whether businesses should be distracted by WAF’s in the first place.  The most important aspect of all this is the functionality that is to be provided by this technology. The WAF requirements outlined in requirement 6.6:

  • Verify that an application-layer firewall is in place in front of web-facing applications to detect and prevent web-based attacks.

Make sure any WAF implementation meets the full extent of the requirement because “detect and prevent web-based attacks” can get a little sticky. As technology goes, there are a few variations in how WAF’s have been developed. Some products use reverse proxying to interrupt the web session for the ‘detect’ and accomplish the ‘prevent’ by only allowing valid sessions. This validation is being done in variations just like typical IDS/IPS’s operation: you get your choice of signatures, anomaly detection, protocol inspection, and combinations thereof. Some of the available products skip the proxy function and monitor the web traffic like a traditional IDS/IPS for known or suspicious threats either in-line or via a SPAN or TAP. Companies can not only choose their type of technology but can also decide on using open-source software or commercially supported products or a cross between the two.

The open-source route offers mod_security for apache and if companies need commercial support, you can get an appliance running mod_security. I found it interesting, in a recent Oracle Application deployment, Oracle recommends the use of mod_security to service as an application-layer firewall and URL-filtering firewall for DMZ-deployments. If mod_security doesn’t fit your needs, Guardian is also an open-sourced software with detection and prevention capabilities. Both have commercial support and product options.

mod_security has some other interesting options. It is possible to take the SNORT web signatures and convert them to mod_security rules via a script provided with mod_security. There are also several groups that provide signatures / rules for mod_security to identity new threats.

Outside the open-source space, there are products like Imperva’s SecureSphere gateways that use anomaly detection and profiling to determine whether something should or should not be allowed to access a web server. This company’s product line features an interesting twist, the dynamic profiling technology relied upon to ‘detect and prevent’ comes from none other than the man that developed ‘stateful packet inspection’ in CheckPoint firewalls.

Along with Imperva, are F5, Cisco, CheckPoint, and the usual list of security vendors ready to snatch up your “bail-out” funding 🙂 . As with any security technology, only after a review of your organizations needs and a thorough pilot of the prospective technology will identify the best-fit for any organization.

At the end of the day, the use of WAF technology to mitigate web application security is but one of the many defenses an organization should have in place to provide data security and data privacy.

What do you use to guard the security of your web applications?

Speeding up PIX Parsing

Recent questions, comments, and suggestions have prompted this post. I would like to collect ideas for improving PIX Logging Architecture or provide a place to point out issues with running PLA at your organization.

If you use PLA or another open-source tool, tell us how you solve logging latency, sluggish reporting, and other related bottleneck issues associated with centralized log collecting and monitoring.