RE: All Port Scans, false positive

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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