Snort mailing list archives
RE: portscan2 and conversation
From: "Kreimendahl, Chad J" <Chad.Kreimendahl () umb com>
Date: Mon, 15 Sep 2003 10:24:24 -0500
I thought so too... but we've experiences the same thing. I believe the issue was that a valid connection counts, since if someone was scanning they may make a valid connection and send data to make it look real. The likely culprit is the lack of keepalives on the server, causing your system to open a new connection for every item to download... thus giving you a new local port and looking like that web server is portscanning you. You could do a portscan-ignoreports-from 80... but then anyone knowing how to set their scanner from source pot 80 would defeat you... -----Original Message----- From: Denny Page [mailto:denny () cococafe com] Sent: Saturday, September 13, 2003 6:03 PM To: Snort Users Subject: [Snort-users] portscan2 and conversation Ok, dumb question time. I have portscan2 set up to ignore hosts from my local network. This appears to work fine for both TCP and UDP. I.E. no alerts from DNS activity, and no alerts from nmaps within the network. Nmaps from outside the network trigger alerts as you would expect. This is all desirable. What is not desirable is that alerts are being triggered by outbound HTTP requests. When visiting a site that is comprised of many individual files such as graphic navigation bars (www.securityfocus.com is one such) , portscan2 reports that the remote HTTP server is executing a portscan on the machine running the browser. Portscan2 appears to be triggering on the inbound SYN-ACK that the HTTP server sends in response to the SYN from the browser. Since the SYN-ACK is being in response to a connection (conversation) initiated by a portscan2 ignored host, I would not expect it to trigger an alert. Isn't this what conversation is for? Am I missing something, or is portscan2 goofy? Thanks for any assistance, Denny ------------------------------------------------------- This sf.net email is sponsored by:ThinkGeek Welcome to geek heaven. http://thinkgeek.com/sf _______________________________________________ Snort-users mailing list Snort-users () lists sourceforge net Go to this URL to change user options or unsubscribe: https://lists.sourceforge.net/lists/listinfo/snort-users Snort-users list archive: http://www.geocrawler.com/redir-sf.php3?list=snort-users ------------------------------------------------------- This sf.net email is sponsored by:ThinkGeek Welcome to geek heaven. http://thinkgeek.com/sf _______________________________________________ Snort-users mailing list Snort-users () lists sourceforge net Go to this URL to change user options or unsubscribe: https://lists.sourceforge.net/lists/listinfo/snort-users Snort-users list archive: http://www.geocrawler.com/redir-sf.php3?list=snort-users
Current thread:
- portscan2 and conversation Denny Page (Sep 13)
- Re: portscan2 and conversation Denny Page (Sep 16)
- <Possible follow-ups>
- RE: portscan2 and conversation Kreimendahl, Chad J (Sep 15)
- Snort don't detect any attack Adriano Frare (Sep 15)