Re: IDS deployment outside FW?

[<templeofprs () hotmail com>]

In-Reply-To: <BAY19-F385a0q6AGvN4000177b6 () hotmail com>

Having your IDS on the outside of your firewalls does not tell you what is getting through your firewalls. It does not 
help you from an IDS perspective... just assume that everything is going to hit the outside of your firewall (every 
random sweep or port scan). If your firewalls are bounded by IDS and you correlate both aspects with your firewall logs 
you have a clearer picture of what your threats look like.

> Dear List
>
> I have moved into an organization that has two RealSecure Network Sensors 
> and a network architecture that is VLANd/DMZd to where localized deployment 
> to capture traffic would require 8 to 12 sensors to avoid bridging loops.
>
> The cheapest/simplest option (without deploying SNORT/Prelude, etc - the 
> organization wants to remain on a single application architecture where 
> possible) is to place the two sensors outside of the firewall.
>
> I understand that this means:
> The sensors will be in hostile territory and need to be maintained to a very 
> high degree
> There will be an operations overhead of dealing with all of the noise that 
> would normally be filtered by a firewall
>
> Does anyone have experience of doing this?
> Are there any other issues that I have not considered?
>
> Chris
>
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