[Snort-users] Flow-portscan oddity

Jasmine CHUA Jasmine.Chua at ...11322...
Thu Apr 15 21:09:03 EDT 2004

Hash: SHA1

Hi all

Flow-Portscan works but not quite well for me. On Acid I only see the very
first portscan alert after restarting snort and barnyard, and thereafter, I
don't get to see the next and the next portscan alert on Acid. Its really

Anyone facing this problem?

- -----Original Message-----
From: Dusty Hall [mailto:halljer at ...8709...]
Sent: Wednesday, April 14, 2004 22:27
To: Todd_Pratt at ...11631...; dmccrea at ...10965...;
Chad.Kreimendahl at ...4716...
Cc: snort-users at lists.sourceforge.net
Subject: RE: [Snort-users] Flow-portscan oddity

I guess I'll chime in...  Flow-Portscan seem to work ok for me but I never
know what port is getting scanned.  Thoughts?

- -Dusty

04/14-14:21:00.987513  [**] [121:1:1] Portscan detected from 161.57.x.x
Talker(fixed: 0 sliding: 0) Scanner(fixed: 16 sliding: 16) [**] 
04/14-14:21:34.725954  [**] [121:1:1] Portscan detected from 204.38.x.x
Talker(fixed: 0 sliding: 0) Scanner(fixed: 16 sliding: 14) [**] 
04/14-14:21:38.207946  [**] [121:1:1] Portscan detected from 12.173.x.x
Talker(fixed: 0 sliding: 0) Scanner(fixed: 15 sliding: 15) [**] 
04/14-14:21:38.347495  [**] [121:1:1] Portscan detected from 12.173.x.x
Talker(fixed: 0 sliding: 0) Scanner(fixed: 40 sliding: 40) [**] 

preprocessor flow-portscan: \
server-watchnet [xxx.xxx.xxx.xxx\xx] \
dst-ignore-net [xxx.xxx.xxx.xxx\xx] \
src-ignore-net [xxx.xxx.xxx.xxx\xx] \
unique-memcap 5000000 unique-rows 50000 \
tcp-penalties on \
server-rows 65535 \
server-scanner-limit 50 \
alert-mode once \
#alert-mode all \
output-mode msg \
#output-mode pktkludge \
server-learning-time 3600

>>> "Kreimendahl, Chad J" <Chad.Kreimendahl at ...4716...> 4/13/2004 4:21:16 PM
I haven't attempted the syslog method of alerting, but I doubt that's
it, being that their alerting method is centralized.  Have you generated
alerts on your own and verified them?

I've just attempted using your config with our setup, and again it did
not see my scans (and no, they did not originate from $HOME_NET).
What's your config for the flow preproc?


From: Todd_Pratt at ...11631... [mailto:Todd_Pratt at ...11631...] 
Sent: Tuesday, April 13, 2004 2:02 PM
To: Douglas McCrea
Cc: Snort Users; snort-users-admin at lists.sourceforge.net 
Subject: RE: [Snort-users] Flow-portscan oddity

flow-portscan works for me.  I get between 20 and 40 alerts per hour.
The only output I use is syslog so I don't know if that makes a

Here's the line I use: 

        preprocessor flow-portscan: alert-mode once src-ignore-net

I'm running 2.1.2 build 25 

Todd Pratt
Systems Security Certified Practitioner
IT Security Administrator
Harte Hanks, Inc.
ph 978-436-3368
tpratt at ...11631... 

"Douglas McCrea" <dmccrea at ...10965...> 
Sent by: snort-users-admin at lists.sourceforge.net 

04/13/2004 11:56 AM 


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