Re: Router / Protocol Problem

[Sam Stickland <sam_mailinglists () spacething org>]

Hi John,

John Kristoff wrote:
> On Thu, 7 Sep 2006 07:27:16 -0400
> "Mike Walter" <mwalter () 3z net> wrote:
>
> > Sep  7 06:50:20.697 EST: %SEC-6-IPACCESSLOGP: list 166 denied tcp
> > 69.50.222.8(25) -> 69.4.74.14(2421), 4 packets
> [...]
> I'm not very familiar with NBAR or how to use it for CodeRed, but this
> first rule:
>
> > access-list 166 deny   ip any any dscp 1 log
>
> Seems dubious.  So I'm not not sure what sets the codepoint to 000001
> by default, but apparently CodeRed does?  Nevertheless, this seems like
> a very weak basis for determining whether something is malicious.

It's his NBAR config lower down that sets the dscp value:

class-map match-any http-hacks
match protocol http url "*default.ida*"
match protocol http url "*cmd.exe*"
match protocol http url "*root.exe*"

policy-map mark-inbound-http-hacks
class http-hacks
set ip dscp 1


So, there's probably two things that could happen here: One, NBAR is 
incorrectly identifying the SMTP traffic as code red, or two, the SMTP 
traffic is already marked with dscp 1. If you've using these values 
internally in your own network then they should be reset on all 
externally received traffic.

Sam