From: Derick Anderson (danderson@vikus.com)
Date: Mon Oct 24 2005 - 14:56:13 EDT
> -----Original Message-----
> From: tarunthenut@gmail.com [mailto:tarunthenut@gmail.com]
> Sent: Monday, October 24, 2005 8:33 AM
> To: pen-test@securityfocus.com
> Subject: Scanning Class A network
>
> Hello All,
> Recently I was given a task to carry out a port scan of an
> entire valid Class A range (Dont ask me what the huge pool of
> valid IP's was for :) ).
> The scan needed to be carried out externally, and not from
> within the network to identify hosts and ports exposed to the
> Internet.
> The problem compounded cause of the following limitations :
> 1. ICMP was not allowed in the network
> 2. The IP range was to be scanned every month for the entire
> port range fro= m
> 1-65535 for TCP & UDP
> After searching for a suitable scanner which could scan such
> a large range in reasonable time, I could think of only nmap,
> nessus, superscan and ISS.
> But because of the limitations stated above,all the tools
> took a huge amount of time (ran into month).
> I have struggled with options within the tools, tried
> configurable parameters (host time out, parallelism, RTT etc)
> and divided into smaller class C networks and scanned.but
> still the scan seems to take ages even if it is Any advise
> would be welcome :)
>
> Cheers
> tarunthenut
>
You have to scan 2,198,989,570,050 ports (16.7 million addresses * 65535
ports * 2 protocols - 131,070 for the network/broadcast addressess,
assuming this is a real Class A and not a bunch of Class B or C's), so
you're looking at nearly 850,000 ports scanned per second (2.2 trillion
/ 30 days / 24 hours / 60 minutes / 60 seconds). Multiply half of that
by the minimum packet size for TCP and the other half for UDP and you'll
get your bandwidth requirement. Then you can tell your superiors that
you've been given an impossible task.
If you are actually dealing with a bunch of Class C's, then the number
goes down a bit, but still...
Derick Anderson
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