[Snort-users] Questions: Filtering ESP & Duplicate traffic
Jason.Haar at ...294...
Tue Mar 24 17:35:59 EDT 2009
Joel Esler wrote:
> As far as filtering out things like ESP and VPN traffic, I see no
> reason to inspect it if it's encrypted. (That's what encryption is
> for right? To make stuff unreadable?)
That's what we do on our sensors. We monitor our (VPN-based) WAN links
with snort, and depending on where the SPAN is done (which depends on
switch type, VLANs and how good a job the network group do in
implementing it), may contain a fair chunk of IPSec/GRE traffic. So we
filter that out to save CPU cycles. Also, where network-based DMZ
backups are done, we filter out the backup apps ports as well - because
otherwise snort gets hammered dealing with all that extreme traffic.
Obviously there is always a price to pay: anything you filter out means
snort cannot detect an issue within that protocol. C'est la vie.
Information Security Manager, Trimble Navigation Ltd.
Phone: +64 3 9635 377 Fax: +64 3 9635 417
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