Challenging the Firewall Data Center Dogma

Do you really need a firewall to secure web and application services? Some organizations would say no based on their experiences while others are sure to quail at the very thought of such an unnatural suggestion.

Firewalls are, in most organizations, the first line of defense for web and application services. This is true whether those services are offered to the public or only to off-site employees via secure remote access. The firewall is, and has been, the primary foundation around which most network security architectures are built.

We’ve spent years designing highly-available, redundant architectures that include the firewall. We’ve deployed them not only at “the edge” but moved them further and further into the data center in architectures that have commonly become known as “firewall sandwiches”. The reasons for this are simple – we want to protect those services that are critical to the business and the primary means by which we accomplish that task is by controlling access to them via often simple but powerful access control.

In later years we’ve come to rely upon additional intrusion detection systems such as IPS (Intrusion Prevention Systems) that are focused on sniffing out (sometimes literally) malicious attacks and attempts to circumvent security policies and stop them.

One of the core attacks against which such solutions protect services is a denial of service.

>Unfortunately, it is increasingly reality that the firewall is neither able to detect or withstand such attacks and ultimately such devices fail – often at a critical moment. The question then is what to do about it. The answer may be to simply remove the firewall from the critical data path for web services./p>

THAT’S UNNATURAL!

Just about anything is unnatural the first time you try it, but that doesn’t mean it isn’t going to work or that it’s necessarily wrong. One of my favorite fantasy series – David Eddings’ Belgariad – illustrates this concept quite nicely. A couple of armies need to move their ships up an escarpment to cross a particular piece of land to get where they need to be. Now usually fording – historically – involves manhandling ships across land. This is hard and takes a lot of time. No one looked forward to this process. In the story, someone is wise enough to put these extremely large ships on wheels and then leverage the power of entire herds of horses to move them over the land, thus improving performance of the process and saving a whole lot of resources. One of the kings is not all that sure he likes violating a precept that has always been akin to dogma – you ford ships by hand.

King Rhodar put on a perfectly straight face. “I’ll be the first to admit that it’s probably not nearly as good as moving them by hand, Anheg. I’m sure there are some rather profound philosophical reasons for all that sweating and grunting and cursing, but it is faster, wouldn’t you say? And we really ought to move right along with this.”
“It’s unnatural,” Anheg growled, still glaring at the two ships, which were already several hundred yards away.
>Rhodar shrugged. “Anything’s unnatural the first time you try it.”
-- “Enchanter’s End Game”, David Eddings (p 147) >

Needless to say King Anheg eventually gave in and allowed his ships to be moved in this new, unnatural way, finding it to be more efficient and faster and ultimately it kept his men from rebelling against him for making them work so hard.

This same lesson can be applied to removing the firewall from the critical inbound data path of services. Sure, it sounds unnatural and perhaps it is if it’s the first time you’re trying it, but necessity is the mother of invention and seems to also help overcome the feeling that something shouldn’t be done because it hasn’t been done before. If you need convincing as to why you might consider such a tactic, consider a recent survey conducted by Arbor Networks showing an increasing failure rate of firewalls and IPS solutions due to attacks.

“Eighty-six percent of respondents indicated that they or their customers have placed stateful firewall and/or IPS devices in their IDCs. Nearly half of all respondents—a solid majority of those who actually have deployed these devices within their IDCs— experienced stateful firewall and/or IPS failure as a direct result of DDoS attacks during the survey period. Only 14 percent indicated that they follow the IDC BCP of enforcing access policy via stateless ACLs deployed on hardware-based routers/Layer 3 switches capable of handling millions of packets per second.”[emphasis added]
>-- Network Infrastructure Security Report Volume VI, Arbor Networks, Feb 1 2011

That is a lot of failures, especially given that firewalls are a critical data center component and are almost certainly in the path of a business critical web or application service.

But it’s dogma; you simply must have a firewall in front of these services. Or do you?

BASIC FIREWALLING ISN’T ENOUGH

The reality is that you need firewall functionality – services - but you also need a lot more. You need to control access to services at the network layers but you also need to mitigate access and attacks occurring at the application layers. That means packet-based firewalls – even with their “deep packet inspection” capabilities – are not necessarily up to the task of protecting the services they’re supposed to be protecting. The Anonymous attacks taught us that attacks are now not only distributed from a client perspective, they’re also distributed from a service perspective; attacking not only the network but the application layers. That means every device between clients and servers must be capable of handling not only the increase in traffic but somehow detecting and preventing those attacks from successfully achieving their goal: denial of service.

During the anonymous attacks, discussions regarding what to do about traffic overwhelming firewalls resulted in what might be considered an “unnatural” solution: removal of the firewall. That’s because the firewall was actually part of the problem, not the solution, and removing it from the inbound data path resulted in a more streamlined (and efficient) route that enabled continuous availability of services despite ongoing attacks – without compromising security.

Yes, you heard that right. Some organizations are running sans firewall and finding that for inbound web services, at least, the streamlined path is maintaining a positive security posture while ensuring availability and performance. That doesn’t mean they are operating without those security services in place, it just means they’ve found that other components in the inbound data path are capable of providing those basic firewalling services without negatively impacting availability.

ATTACKS AREN’T the ONLY PROBLEM

It isn’t just attacks that are going to pose problems in the near future for firewalls and IPS components. The increase in attacks and attack surfaces are alarming, yes, but it’s that combined with an increase in traffic in general that’s pushing load on all data center components off the charts. Cisco recently shared the results of its latest Visual Networking Index Forecast:

“By 2015, Cisco says that mobile data traffic will grow to 6.3 exabytes of data or about 1 billion gigabytes of data per month. The report indicates that two-thirds of the mobile data traffic on carrier networks in 2015 will come from video services. This trend follows a similar trend in traditional broadband traffic growth.”
>Read more: http://news.cnet.com/8301-30686_3-20030291-266.html#ixzz1CtYWZPAk

Cisco’s report is obviously focused on service providers as they will bear the brunt of the increase in traffic (and in many cases they bear the majority of the impact from denial of service attacks) but that traffic is going somewhere, and somewhere is often your data center, accessing your services, increasing load on your data center infrastructure.

Load testing, to be sure, of an active architecture is important. It’s the only way to really determine what the real capacity for your data center will be and how it will respond under heavy load – and that includes the additional strain resulting from an attack. Cloud-based load testing services are available and can certainly be of assistance in performing such testing on live infrastructure. And yes, it has to be live or it won’t find all the cracks and fissures in your architecture. It isn’t your lab environment, after all, that’s going to be under attack or stressed out by sudden surges in traffic. Perhaps no problems exist, but you really don’t want to find out there are when the pressure’s on and you have to make the decision in the heat of the moment. Try testing with your firewall, and without (assuming you have solutions capable of providing the security services required in the inbound data path). See if there is an impact (positive or negative) and then you’ll be better able to make a decision in the event it becomes necessary.

Putting firewalls in front of your Internet services has been dogma for a long, long time. But are they up to the task? It would appear in many cases they aren’t. When a solid majority of folks have found their sites down due to firewall failure, we may need to rethink the role of a firewall in securing services. That doesn’t mean we’ll come to a different conclusion, especially as only part of the architectural decisions made regarding data center security are dependent on technological considerations; other factors such as risk tolerance by the business are often the driving factor and play a much larger role in such decisions whether IT likes it or not. But it does mean that we should occasionally re-evaluate our data center strategies and consider whether traditional architectural dogma is still appropriate in today’s environment. Especially when that architectural dogma may be part of the problem.

Published Feb 16, 2011

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