Security Basics: Re: Network discovery

[Byron Sonne <blsonne () rogers com>]

> I would like to ask all of you, if you have every used a network discovery
> tool? I have a network with more than 5000 PC's and more than 70 sites in
> the country. I would like to create an analysis about the network nodes,
> line between them, speed of the lines etc. Would it be possible with a tool
> to discover the whole internal network, with routers, gateways and all the
> important datas?
No.

You could run a number of utilities/programs which will enumerate 
alot/most of the devices on your network and provide quite a bit of 
information.
It will help you compose a map, but nothing that you can plop on a 
computer and run or plug into your network will give you a truly good 
map unless your network is configured perfectly, uses common hardware, 
has a fairly vanilla config, etc. Even then, I seriously doubt you'll 
get a complete picture. I think bad information is worse than no 
information at all as it can lead you to make false assumptions. Also, 
consider the case that if *you* can get all the information, perhaps a 
*cracker* (which is what most people mean when they abuse and misuse the 
term 'hacker') could too.
But I digress... there are a number of gotchas you must be aware of. 
Some of these gotchas are:
(1) devices that only listen; they don't transmit on the network. Not 
just sniffers.
(2) Filtering or Translating proxies of whatever description.
(3) NAT (Network Address Translation)
(4) Firewalls
(5) Custom hardware/software/protocols
(6) Encryption
(7) Temporary power or network outages
(8) Design deficiencies in standard network protocols

Some things that can help out alot are:
(a) Good documentation
(b) Well labelled cabling and devices
(c) A sane overall architecture
(d) Good, knowledgeable people
(e) Good tools. Good starter link: http://www.insecure.org/tools.html
(f) Things like Cisco CDP, etc.

You and your skills are the most important thing of all, so read and 
learn as much as possible.
Regards,
Byron Sonne


--

For Good, return Good. For Evil, return Justice.


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