full-disclosure - ICMP (was: daily internet traffic report)

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From: frankdewit at home.nl (Frank de Wit)
Subject: ICMP (was: daily internet traffic report)

I thought I asked a question ; the answer 'yes' should have been 
sufficient ;-)
Just joking, let's ask two other questions:
-when you read about ICMP fingerprinting (see Ofir Arkin's great articles)
-and you see tools like Xprobe and a lot of other OS-fingerprinting tools
I might be wrong, but:
a) do you still think ICMP is a good thing in relation to security (by 
obscurity)?
b) why would you need ICMP from the internet to your perimeter/DMZ-devices?

Hojje, Frank

Willem Koenings wrote:

> 
>  
>
>>are they? 
>>do you remember 'firewalking'? 
>>    
>>
>
>sorry, but firewalking is not icmp-only technique and don't
>use full range of icmp types/codes.
>by firewalking you use tcp or udp packets (depends, which
>protocol acl you want to study) with one bigger TTL than
>target and monitor results via icmp type 11.
>
>if you really afraid firewalking, then instead of closing
>down all icmp you can close down only type 11. and nat
>firewall protects you from firewalking anyway.
>
>what i want to say? blindly closing down things is easiest
>thing to do. but doing so you are not on the top of the problem
>and you don't control things. get down to the problem and fix
>things. there's one too many black hole routers in the world
>and availability is also an security attribute.
>
>al the best,
>
>W.
>  
>