RE: All Port Scans, false positive
- From: "Amy Babinchak" <amy@xxxxxxxxxxxxxxxxxxxxxxxxxx>
- To: "[ISAserver.org Discussion List]" <isalist@xxxxxxxxxxxxx>
- Date: Wed, 14 Sep 2005 13:28:20 -0400
What does RST stand for?
Amy
Harbor Computer Services
Small Business Computer Specialists
Client Blog: http://smalltechnotes.blogspot.com/
Tech Blog: http://isainsbs.blogspot.com/
Website: http://www.harborcomputerservices.net/
-----Original Message-----
From: Jim Harrison [mailto:Jim@xxxxxxxxxxxx]
Sent: Wednesday, September 14, 2005 1:25 PM
To: [ISAserver.org Discussion List]
Subject: [isalist] RE: All Port Scans, false positive
http://www.ISAserver.org
Possible, but the most likely reason is the "late packet" scenario I've
described before.
IE and some web services are very rude on the wire. Instead of closing a
session with a nice, friendly FIN-ACK sequence, they RST the connection.
If this happens before the other side has responded to a previous
communication, ISA will have closed the connection and will see the response
packet as an "all port scan" because it is destined for a port on the ephemeral
range.
You can validate this by examining your ISA logs for previous communication
between ISA and the source of the "scan".
Odds are, it's listed as a source port used between ISA and the "scan" source
in a previous communication.
-----Original Message-----
From: Ball, Dan [mailto:DBall@xxxxxxxxxxx]
Sent: Wednesday, September 14, 2005 9:51 AM
To: [ISAserver.org Discussion List]
Subject: [isalist] RE: All Port Scans, false positive
http://www.ISAserver.org
http://www.ISAserver.org
A hacked router is one example...
I'm not sure if I'm correct on this, but I understand it as an "All Port" scan
in ISA actually means there 20 (default setting) ports scanned in quick
succession, it doesn't necessarily mean ALL ports were tried. The setting for
this is in the "Configuration->General->Enable Intrusion Detection and DNS
Attack Detection" menu.
________________________________
From: Amy Babinchak [mailto:amy@xxxxxxxxxxxxxxxxxxxxxxxxxx]
Sent: Wednesday, September 14, 2005 12:30 PM
To: [ISAserver.org Discussion List]
Subject: [isalist] All Port Scans, false positive
http://www.ISAserver.org
http://www.ISAserver.org
A question comes to me and I don't have the answer but I know that you guys
will. If I have a router in front of my ISA/SBS server that only allows 4 ports
through, how is it that all port scans are reported from IP addresses at
Microsoft and the ISP on my ISA server? Is it a false positive? If so, what in
the world causes it when there are only 4 accessible ports?
Amy
Harbor Computer Services
Small Business Computer Specialists
Client Blog: http://smalltechnotes.blogspot.com/
Tech Blog: http://isainsbs.blogspot.com/
Website: http://www.harborcomputerservices.net/
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