This is a guest blog post. Views expressed in this post are original thoughts posted by Glen Kemp, Solutions Consultant at SecureData Europe. These views are his own and in no way do they represent the views of the company he works for.
Firewalls are like dairy products; they don’t stay fresh for long. Decisions made during your last platform refresh or even initial design won’t necessarily ring true once any time has passed. The reality of enterprise networking is that the final link in the “design – implement – operate – analyse –design” life cycle doesn’t happen anywhere near often enough. The fact is the design and implementation stages of a project are almost always hurried to get into the operational phase as soon as humanly possible. The analysis which goes back into the design only tends to happen when there is a significant failure or an external motivating factor (such as the end of life of the NetScreen 25). If you are going to take the leap and migrate from ScreenOS to a Junos platform; it’s worth revisiting the original design and the assumptions made insofar of the technology chosen; the capacity of the network and the level of resiliency required. It is very likely that if you were to take your current requirements and create a design based around them, your network would look nothing like it does at the moment. Given that for many organisations no infrastructure changes are made without a supporting project code and associated CAPEX, there are few other opportunities to fix the things which aren’t as they should be.
So, Carpe Diem people; it’s time for some security spring cleaning (ok, autumnal) of your Internet facing infrastructure. A firewall policy review pretty much goes without saying. Tomes have been written and there are commercial products which will automate it, but no-one knows your network better than you. Even when faced with a nine hundred rule monster, it’s worth spending the time and weeding out what you can. Most firewall administrators log pretty much everything by default, so it’s not normally that hard to detect which rules are infrequently matched.
Top candidates for removal:
The physical configuration of interfaces is frequently overlooked, depending on the age of your infrastructure there is chance there are 100mb switches (or even hubs!) kicking around your Demilitarised Zones (DMZ). Given the price of switching, they need to go. Another classic is the permeation of Virtual Hosts on physical DMZs. No-one ever seems to want to make a decision as to whether these hosts should be trunked from the core or have one-to-one mapping to a physical interface, so I usually see both. For the sake of efficiency most just use trunked DMZs; but it’s worth revisiting every instance where you have this physical/logical dilemma and standardising the approach.
There are a probably a hundred crazy things that will be unique to your organisation which need some sort of attention. It’s worth asking some additional questions: Is an ASIC based design still vital? Do I need interface level resiliency and how many physicals should I dedicate to clustering? Once you’ve identified the answers this can be fed into the “What our network should look like” design, which then influences technology you may ultimately adopt.
Doing a straight technology like-for-like swap may be the path of least resistance, but not doing a proper analysis is a missed opportunity to get your network into better shape and better able to cope with shifting requirements and priorities. Get it right, no-one will notice; get it wrong (or don’t even try) and be prepared to be spending more time with the office coffee machine than your kids! Now to get all interactive like a 1990’s Multimedia CD-ROM; I’d be interested in the horrors you’ve uncovered during a firewall migration; Internet Router connected to the core for “convenience”? All networks on the same Zone with “Block Intra-zone Traffic” disabled? Home Broadband IP of “sacked in disgrace firewall admin” in the “manager-ip” list? I’m sure you’ve found worse.
Discussing a wide range of topics impacting enterprises and data center security.