[Dshield] ISPs - How much monitoring is enough?

Micheal Patterson micheal at tsgincorporated.com
Thu Jan 15 20:27:43 GMT 2004

----- Original Message ----- 
From: "Bjorn Stromberg" <bjorn at thechemistrylab.com>
To: <list at dshield.org>
Sent: Thursday, January 15, 2004 12:47 PM
Subject: [Dshield] ISPs - How much monitoring is enough?

> I've got 4 static IP addresses assigned to a server that is always on. My
> ISP sends out a daily sweep from pinging each of my IPs and
> sending an ACK packet to Port 80 on each of my IPs. Recently, around
> christmas they began hourly ping sweeps from the gateway router, these
> been filling up my log files ever since. Today added a rule to my firewall
> to respond to these hourly pings and stop blocking them.
> What's the best practice in this scenario? Do I continue to block the
> pings and log them? Do I silently block them? or Do I accept them and
> respond?
> Obviously these packets from appear to be forged because they
> coming in on the internet side of my firewall. They get dropped and a
> flag gets raised because these are supposed to be non-routable IPs.
> Does your ISP do similar things? Do you receive hourly ping sweeps? Daily
> ping sweeps? No ping sweeps at all?
> Does your ISP scan well known ports for compromised machines?
> I feel it's a bit much to be constantly bombarded by skiddies and to have
> ISP join in on the action is, for lack of a better word, annoying.
> Bjorn Stromberg

Bjorn, there's a strong possibility that their internal network is running
off of the 10/8 iprange. This isn't so uncommon. It keeps them from getting
targeted from off net. To your router, they're non-routable IP's, however to
their router, it's probably quite local to them depending on the type of
circuit your link is. This is a common practice with Cable and DSL service
providers. They'll use a 10/8, 192.168/16, etc on their local network, give
you the public IP and just static route traffic or put the cpe stuff in
bridge mode.


Micheal Patterson
TSG Network Administration

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