Re: Cable Vs. DSL

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Date: 30 Apr 2003 16:38:55 -0000
To: security-basics@securityfocus.com

Well, its likely that he is using a Linksys or D-link NAT enabled router,
which in that case is pretty secure because these routers are also
stateful packet filters.

So in short, yes your clients are pretty secure as long as you are not
port forwarding services internally, in which you open yourself up to
whatever vulnerabilities exist on the running internal services. If you
don't have a lot of clients, it would be a good idea to set your IP's up
statically, and filter unused IP's and MAC addresses at the router - this
would help if you had a case of IP spoofing, it would also make it a
little easier in internal log analysis.

>Since the router's address is seen as one address from outside, and
>there's no "host" at that IP address, and it is administered at an
internal
>address inside the network, is there any way for an intruder to
compromise
>my network and get to any of my client machines?

There are ways, as I mentioned above, the most obvious being port
forwards. Other then that, make sure remote management is not accessible
from the outside, and make sure you are running the latest firmware. Also
make sure your WAN port is set to block unsolicited requests. If you are
just a home user, I wouldn't worry about predictable TCP ISN #'s or
firewalking - unless you specifically have someone targeting you who is
very very determined. If your router has the functionality, its generally
a good idea to block all ICMP (outbound, block ICMP Destination
Unreachable).

Jesse

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>From: "Chris Berry" <compjma@hotmail.com>
>To: security-basics@securityfocus.com
>Subject: Re: Cable Vs. DSL
>Date: Mon, 28 Apr 2003 19:20:12 -0700
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>
>>From: Greg Tracy <greg@sixx.com>
>>Here's a question (I'm relatively new at this).
>
>Well, you're in the right place, that's a good start.
>
>>I have a cable connection, with a broadband NAT router which acts as a
>>DHCP server for a variety of clients (Mac, Win2K and Linux). All the
>>machines are given an internal IP address (like the old class C
>>addresses) and the router has the address assigned by the ISP, which
>>is what the clients are seen to have from the internet.
>
>So basically what you're saying is that you have one public IP address
and
>the rest are private non-publicly routable ones divided by your NAT
enabled
>router.
>
>>Since the router's address is seen as one address from outside, and
>>there's no "host" at that IP address, and it is administered at an
internal
>>address inside the network, is there any way for an intruder to
compromise
>>my network and get to any of my client machines?
>
>In short, yes, lots of ways.
>
>>Is this the best way (other than using a firewall, or in addition to) to
>>make this connection more secure?
>
>NAT basically provides you with about as much security as your mp3
player,
>which is to say none at all. This is because NAT is not designed as a
>security measure, it's merely a way to broaden the available address
pool.
>Here are some basic measures I'd recommend to secure your network:
>
>1) Firewall
>2) Anti-Virus
>3) Spyware detector for your windows machines (I like SpybotSD)
>4) Decent passwords on your systems
>
>Depending on your level of paranoia, there's lots more.
>
>Chris Berry
>compjma@hotmail.com
>Systems Administrator
>JM Associates
>
>"Without change, something sleeps inside us, and seldom awakens. The
>sleeper must awaken." -- Duke Leto Atreides
>
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prospectus based upon the core principle concepts of security. This ALL INCLUSIVE curriculum utilizes lectures, case studies and true hands-on utilization 
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