RE: [logs] NBS

From: Williams Jon (WilliamsJonathan@private)
Date: Fri Sep 03 2004 - 10:54:42 PDT

I'm not usually one to gush, but this tool is way freakin' cool!  I've
already got it set up monitoring for new services in my production
networks, and my mind is reeling with the possibilities.

Couple suggestions, though.  I've got enough stuff going on (been
running it for ten minutes, have got nearly 1000 unique server ip/port
combinations, over 500 unique servers, and around 200 unique service
ports) that just doing the Top X or Bottom X or Last X doesn't show me
the interesting things.  I'd like to be able to show, for example, those
things that have more than one hit but less than 100 in the last hour,
for example.  Or maybe a report that shows the things with one hit
between 17:00 and 23:00 last night.  Stuff like that.

Also, my input is coming from a script that does a tcpdump in a loop,
but if I just pipe the output directly to nbs, nbsdump blocks until I
end the script.  For example, if I do:

tcpdump -i bge1 -c 100000 -n "tcp[13] &0x3f = 18" |
/usr/local/scripts/nbs/ | nbs -s -d servers

then my nbsdump command will block until I stop the tcpdump.  If, on the
other hand, I have my tcpdump run as:

/usr/sbin/tcpdump -i bge1 -c 10000 -n "tcp[13] &0x3f = 18 |
/usr/local/scripts/nbs/ >/home/nbs/servers.txt; /bin/cat
/home/nbs/servers.txt | /usr/local/bin/nbs -s -d /home/nbs/servers

then nbsdump completes immediately (albeit the output doesn't change
until the tcpdump exits and restarts).  Probably not a big deal, but it
took me an hour of experimenting before I figured out how to deal with

BTW, in case anybody's wondering the BPF I'm using will show only
packets that have the only the TCP flags SYN and ACK set, indicating a
successful connection to a service.  My script pulls out
the source field, which is in the format of %d.%d.%d.%d.%d, where the
first 4 INTs are the IP address and the 5th one is the port.  I'm using
DJB's daemontools to handle restarting the tcpdump.

Hmm.  I wonder if there's a way to set this up to detect Internet
clients that connect to a variety of servers one time each???  <runs
back to keyboard, smiling freakishly>


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