Re: Isolating internal servers behind firewalls

["Behm, Jeffrey L." <BehmJL () bv com>]

You may end up opening up so much stuff in the firewall(s) that they
pretty much become swiss cheese anyways. And much of the stuff you would
open up, would be the same things that would be used as an attack
vector.

How many new exploits come in via chargen nowadays, which you could
block vs. how many come in via Microsoft networking (Ports 445, 137,
139, etc.), which you would have open, if you want file shares to work. 

If you find you have a hacked firewall, you have much bigger problems
than broken access from clients to servers.

That centralized maintenance the security group wants *can* be a pain in
the rearend, depending on how dynamic your environment is, whether you
let just anyone come in and get a DHCP address, etc. Who's
watching/auditing the security group to ensure they are implementing
everything correctly. That maintenance, when it does become such a pain,
always gets migrated down to the low man on the totem pole, where there
is a greater risk of improper implementation. I.E. You probably won't
have the senior InfoSec guy implementing rules for individual
users/machines; That's the new guy's job, and Mr. BigShot doesn't have
time for such menial maintenance.

It's a trade-off between securing down to the gnat's-rearend at
additional cost/maintenance vs. having "adequate" security at lower cost
& easier maintenance. And don't forget that there's always the layer 8
requirements to deal with based on what just came out in E-Week.

Jeff (Disclaimer: My opinions are my own, and do not necessarily reflect
those of any other entity)

On Monday, May 07, 2007 2:35 PM, Dan Lynch said:

How prevalent is it to segregate internal use servers away from internal
clients behind firewalls? What benefits might we gain from the practice?
What threats are we protected from?

The firewall/security group argues that servers and clients should exist
in separate security zones, and that consolidating servers behind
firewalls allows us to 
- Control which clients connect to which servers on what ports
- Centralized administration of that network access
- Centralized logging of network access
- a single point for intrusion detection and prevention measures

These benefits protect us from risk associated with internal attackers
and infected mobile devices or vendor workstations.

On the other hand, the server team counters that 

- troubleshooting problems becomes more difficult 
- firewall restrictions on which workstations can perform administration
makes general maintenance inconvenient, esp. in an emergency
- the threats we're countering are exceedingly rare
- a broken (or hacked) firewall config breaks all access to servers if
consolidated behind firewalls 

Any and all thoughts are appreciated.
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