RE: Port Scans
- From: "Ball, Dan" <DBall@xxxxxxxxxxx>
- To: "[ISAserver.org Discussion List]" <isalist@xxxxxxxxxxxxx>
- Date: Thu, 17 Mar 2005 08:31:30 -0500
Interesting idea, I turned it off on my system, as it doesn't seem like
it would cause harm to have it disabled, and might result in a few less
alerts (Will be waiting for Tom's analysis on it to see what he finds
out.). Thanks for the suggestion!
As a bit of clarification, if you look back through the thread, I never
said I was concerned about external IPs doing port scans, I'm just happy
they're being blocked. In fact, my DNS comment was in response to
someone asking if they should block ALL IPs that generate those alerts.
My doors are locked (Heck, that's why I'm running ISA server), and I
realize that you can't block everyone that might scan you once or twice,
as it would fast become a full-time effort, only to cut down on your
functionality in the long fun (i.e. if you end up blocking DNS servers).
In my original post, I was worried about the ones that were listed as
coming from internal IPs, and wondering if those attacks could be
spoofed. I have found a couple of workstations infected with spyware
that might have been the culprit of some of those alerts, but there were
several instances where I could find no reason for the alert, or
additional proof that it even happened.
________________________________
From: Steve Lunn [mailto:Steve.Lunn@xxxxxxxxxxxxxxxx]
Sent: Thursday, March 17, 2005 04:35
To: [ISAserver.org Discussion List]
Subject: [isalist] RE: Port Scans
http://www.ISAserver.org
Aha, I think I know what this is, as I encountered something similar
using ISA2k.
If you go to the properties of your Internet NIC, into TCP/IP Properties
and click the Advanced button. On the DNS tab at the bottom, there's
an option "Register this connection's address in DNS". IIRC this is
enabled by default, and the result is your external NIC trying to
register
with the External DNS server. This in return initiates a barrage on
incoming packets from the DNS server.
By unchecking the box your server stops trying to register with the
external DNS. While this might only stop the packet scans from the
DNS Servers, it's one less alert to worry about. As Ara rightly says,
lock your door, it's the world we live in.
I get loads of users who have installed personal firewalls coming to
me panicking about all the external attacks that their firewall has
warned them of, so my usual reply is to be worried of the ones it
doesn't warn you of... *evil*
HTH
Regards,
Steve
Steve Lunn - PC & Network Support
Microsoft MCP
DDI: 01423 855101
Fax: 01423 855181
-----Original Message-----
From: Ball, Dan [mailto:DBall@xxxxxxxxxxx]
Sent: 16 March 2005 18:59
To: [ISAserver.org Discussion List]
Subject: [isalist] RE: Port Scans
http://www.ISAserver.org
Depends on what IP the scanning is coming from. For example, I just
noticed a scanning alert today that said it was coming from the IP
address of our ISP's DNS server. If I block that, I will no longer be
able to do DNS lookups.
-----Original Message-----
From: Paul Laudenslager [mailto:paul@xxxxxxxxxxxx]
Sent: Wednesday, March 16, 2005 12:54
To: [ISAserver.org Discussion List]
Subject: [isalist] RE: Port Scans
http://www.ISAserver.org
I see continual port scans from my ISP where I host my servers.
Is it possible to block these IP's altogether?
Thanks!
Paul
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