Archive for the ‘Monitoring’ Category

Ourmon to detect UDP Flood

Saturday, March 15th, 2008

Using graph to detect anomaly has been one of the great features in Ourmon. This is an example why it is great.

If you have been following this blog, you will notice I have 2 posts (including this) that have the strange traffic spike in the nighttime, and it also means that it is good time to attack when everyone is sleeping.
So, there was UDP flood attack on my network in the nighttime yesterday. By checking on Ourmon graphs and reports, I could identify the attack almost immediately without running any other tools.

This is how I identified the UDP flood attack, normally my network will not generate high UDP traffic.

UDP Flood Graph

Do you notice the TCP traffic spike from 2100 to 2200 which is marked in Pink color? I used the same method which I have mentioned previously to check the traffic spike with Argus. It was a inter network file transfer which was running at load 19,001,224 (bits/sec).

Notice the high port ICMP unreachable?

UDP Flood ICMP Unreachable Graph

From UDP Top report, I could see when and which IP launched UDP flood attack, and the time of the attack was stopped.

UDP Top Report

From UDP summarization Top Source IP report:

UDP Top Source IP Report

It is nice that we have not seen any large UDP traffic coming to our network after these IPs were blocked in Firewall.

Ourmon drops packets on 64 bit machine - Fixed

Monday, March 10th, 2008

I mentioned I had Ourmon v2.7 installed previously but it generated a lot packets drop at peaks. I thought it was just my machine’s (Quad core Xeon) fault, which is running FreeBSD AMD64 (64 bit).
I have then installed the latest version of Ourmon (v2.8) which has the experimental threaded support and hoped it would run better in threaded but after the compilation and tested for some time, the problem did not seem to go away.

The CPU usage when I run it in T3 (4 threaded), notice the high CPU usage?

  PID USERNAME  THR PRI   NICE   SIZE    RES STATE  C   TIME   WCPU COMMAND
48707   root           1    121    0      193M   162M CPU5   5   1:41   93.49% ourmon
48706   root           1    121    0      193M   162M CPU2   2   1:35   91.82% ourmon
48705   root           1    120    0      193M   162M CPU7   7   1:37   90.31% ourmon
48708   root           1    121    0      193M   162M CPU3   3   1:31   90.31% ourmon

Ourmon seemed to generate incorrect packet per second graph for me too:
Packet per second before Fix

The bpfstat information:

  pid   	netif  flags       recv     drop      match      sblen 	   hblen   command
48705     em1  p--s-     240244 67980     240244 16777175 16777098 ourmon
48705     em1  p--s-     270156 86341     270156   248714        0          ourmon

There was same problem when I run Ourmon without threaded support:
i386 usage:

  PID USERNAME  THR PRI   NICE   SIZE    RES  STATE  C   TIME   WCPU COMMAND
 1100      root        1      -58    0   24932K 24416K bpf    0  37.2H    1.90% ourmon

AMD64 usage:

  PID USERNAME  THR PRI   NICE   SIZE    RES   STATE  C    TIME   WCPU COMMAND
38236     root        1      109    0     172M   168M  CPU2   2  355:15 70.46% ourmon

I have contacted Jim, the project admin of Ourmon on this issue.
After we have tested for 2 days, I noticed after I have disabled topn_icmperror, topn_scans, and topn_port_scans modules in ourmon.conf, Ourmon has not dropped any packets at peaks.

I reported my findings to Jim and he seemed to find out the problem which caused the Ourmon to drop packet in 64bit machine:

on x86, unsigned int is 4 bytes, unsigned long is 4 bytes
on amd64, unsigned int is 4 bytes, unsigned long is 8 bytes

He sent me a new fixed package and it has been running fine after compilation. Here is the resouce usage with default ourmon.conf on 64 bit:

  PID USERNAME  THR PRI   NICE   SIZE     RES    STATE  C    TIME   WCPU COMMAND
39548     root        1      -58    0   51164K 29752K    bpf    1  15:29    3.96%  ourmon

The pkts graph is displaying correct result now:
Packet per second After Fixed

Jim said this fix will be included in Ourmon v2.9, and it will come with a couple of new features as well.
While we wait for the new package now, it is time to test the blacklist features in v2.8.
Thanks Jim!

Argus to check traffic spike

Saturday, March 8th, 2008

When I checked my Ourmon graph today, I noticed same spike happened at the same time in 2 days.
Usually I don’t really pay attention if there is little spike in the nighttime, but it is not normal when it happened continuously at the same time in 2 days.

Late night traffic spike

Since I have full network traffic log, I converted the tcpdump traffic to Argus flow.

 [root@nsm /nsmdir/2008-03-08]# argus -r snort.log.time -w argus.out 

The traffic spike was neither generated from port 25 nor port 80, I used racluster to merge the status records from the same flow without traffic of port 25 and 80, then piped to rasort to sort (-m) the total count of the packet transaction. -s option is to select and show the fields you want to print, -L0 is used to show the labels. Here is the result:

[root@nsm /nsmdir/2008-03-08]# racluster -nnr argus.out -w - - not port 80 and not port 25 | rasort -nnr - -m pkts -s +1ltime +load +bytes +rate -L0 | less

        StartTime           LastTime    	 Flgs   Proto            SrcAddr  Sport    Dir       DstAddr  Dport     TotPkts   TotBytes       State     Load   TotBytes         Rate
   03:27:47.764771    03:33:46.183595  e sD        6     192.168.134.56.39448     ->     10.2.3.102.46743   2501219 1031277512   FIN 23018378 1031277512  6978.480957
   03:33:46.708627    03:37:43.800844  e sD        6     192.168.134.56.40071     ->     10.2.3.102.16396    526755  543955768   FIN 18354234  543955768  2221.730469
   03:31:51.398870    03:33:15.015036  e sD        6     192.168.134.56.39880     ->     10.2.3.102.32666    212332  219148920   FIN 20967134  219148920  2539.365479
   03:21:43.412374    03:41:50.372550  e sD        6       192.168.200.77.4105    < ? >  10.2.3.102.38327     68916   56532894   CON 374712.5   56532894    57.098816

10.2.3.102 is one of the hosts in my network, so from the packet count and total bytes information, I could identify the spike was generated by which host. You may sort based on other criterias to get the result you want, as there might be flows from different IP with little packet count, with large bandwidth transfer rate (load).

To check the traffic, I used ra to show the flow:

[root@nsm /nsmdir/2008-03-08]# ra -nnr argus.out -L0 - host 192.168.134.56 | less

         StartTime    Flgs  Proto            SrcAddr  Sport   Dir            DstAddr  Dport  TotPkts   TotBytes State
   03:27:46.938889  e           6     192.168.134.56.39446     ->     10.2.3.102.21           16       1464   CON
   03:27:47.537244  e           6     192.168.134.56.39447     ->     10.2.3.102.21           22       1964   CON
   03:27:47.764771  e s         6     192.168.134.56.39448     ->     10.2.3.102.46743     36705   15095192   CON
   03:27:52.764922  e sD        6     192.168.134.56.39448     ->     10.2.3.102.46743     30281   12522592   CON
   03:27:57.765092  e iD        6     192.168.134.56.39448     ->     10.2.3.102.46743     14032    5782634   CON
   03:28:02.765262  e sD        6     192.168.134.56.39448     ->     10.2.3.102.46743     41270   17023976   CON

This seems like a passive FTP transfer for me (by checking the src ports), so I logged on to server to check for the FTP log to verify:

Mar  8 03:33:10 server ftpd: (mm@xxx.com@192.168.134.56) [NOTICE] /home/xxx/public_html/mm//xxx.com_2008.03.08_03-31-02 uploaded  (207309250 bytes, 2444.40KB/sec)
Mar  8 03:33:42 server ftpd: (backup@xxx.com@192.168.134.56) [NOTICE] /home/xxx/backup//xxx.com_2008.03.08_03-21-02 uploaded  (891289600 bytes, 2428.22KB/sec)
Mar  8 03:37:39 server ftpd: (backup@xxx.com@192.168.134.56) [NOTICE] /home/xxx/backup//xxx.com_2008.03.08_03-21-02.001 uploaded  (514473734 bytes, 2121.01KB/sec)

The log information explains all. There was a new job which was setup recently, running at every 3.30 AM to transfer the backup files to host 10.2.3.102.

I do have traffic grapher to check which ports generated the spike but that is another story which is not worth for a blog post.

Ourmon 2.8 on FreeBSD 7.0-RELEASE

Monday, March 3rd, 2008

FreeBSD LogoFreeBSD Team announced the release of FreeBSD 7.0-REL recently which introduces many new features and improvements. There is significant performance improvement for FreeBSD on those multi core systems and it has 15% better performance than best performing Linux kernel. I can’t wait to turn all my NSM sensors which are running on FreeBSD 6.2-REL to 7.0-REL.

Before that, Ourmon, the network monitoring and anomaly detection system had released version 2.8, which introduces a few exciting features as well. The most wanted THREADED (for me) feature is supported now. Although it is still under experimental and only x86(amd compatible) primitive is used for spinlocks, I will definitely give it a try on Quad core NSM sensor(AMD64) which has Ourmon disabled due to massive packets dropped during peak hours.

Ourmon graph:
Ourmon

The installation is pretty straight forward and easy since you just have to run configure.pl and change the home net address. Some people may want to change their network interface and web directory during installation, but the rest settings are default or being auto detected.

This is my installation of Ourmon 2.8 on FreeBSD 7.0-REL.
1. Install libpcre from ports. (/usr/ports/devel/pcre)
2. Install libpcap from ports. (/usr/ports/net/libpcap)
3. Install rrdtool from ports (/usr/ports/databases/rrdtool)
4. Install apache from ports. (/usr/ports/www/apache13, 20, or 22)
5. Run ourmon’s configure.pl.

Here is the output.

# ./configure.pl
configuration script to install ourmon.
note: default is suggested like so: [default]
note: just hit carriage-return for default actions
---------------------------------------------------
Would you like to install the ourmon probe? [y]
Front-end configuration phase started ####################
pcap in general needs to be reinstalled from www.tcpdump.org before ourmon install
found pcap lib in /usr/local/lib/libpcap.a - which is a good thing
hit CR to continue:

Would you like to compile/install ourmon? [y]
ourmon build: using make -f Makefile.bsd LIBS=/usr/local/lib/libpcre.a /usr/local/lib/libpcap.a
`ourmon' is up to date.

Next we determine the ourmon config/filter file to use.
By default, we use the local /usr/local/mrourmon/etc/ourmon.conf to provide input filters to ourmon.
WARNING: you should read/edit/understand ourmon.conf!
Do you want to use another ourmon.conf file in some other directory than /usr/local/mrourmon/etc? [n]

Next we suggest one modification to the ourmon.conf file.

If this is a default install, you should change the following config directive:

        topn_syn_homeip network/netmask

and set it to your home network and mask (A.B.C.D/maskbits style)
Do you want to change the topn_syn home network address? [y]
note: the home net address may be a subnet or host address (/32).
enter a home net address and mask. [127.0.0.1/32] 192.168.1.0/24
netmask: 192.168.1.0/24

Do you want to install the ourmon startup script in the ourmon bin? [y]
WARNING: the default for the interface may not be what you want.
WARNING: use #ifconfig -a to determine interfaces.
Please enter the input interface name to sniff from: [le0]
input interface is le0

Please enter directory for probe output files (mon.lite, etc.): [/usr/local/mrourmon/tmp]
probe output directory name is: /usr/local/mrourmon/tmp

Creating bin/ourmon.sh driver for startup of ourmon.
ourmon.sh placed in ourmon bin for ourmon front-end/probe startup
./ourmon.sh start

copy the startup script (bin/ourmon.sh) to /usr/local/etc/rc.d for boot startup? [y]
ourmon front-end install complete
ourmon front-end build worked

You should now run /usr/local/mrourmon/bin/ourmon.sh to start ourmon

e.g., # /usr/local/mrourmon/bin/ourmon.sh start

You can use ourmon.sh stop to stop ourmon

part 2: install the back-end, omupdate.pl, etc. (web part)? [y]
Back-end configuration phase started ######################################
We need a local web directory for generated web output.
hint: the webpath given here is a guess: give the CORRECT base web directory with /ourmon at the end
enter absolute web server web path directory: [/usr/local/www/data/ourmon] /usr/local/www/ourmon
your output web path is: /usr/local/www/ourmon

Do you want to create the web directory for ourmon?
HINT: good idea if it doesn't exist. [y]
mkdir: /usr/local/www/ourmon: File exists
ln: web.pages: File exists
cp bard/* /usr/local/www/ourmon/bard
cp batchip.sh batchipall.sh omupdate.sh /usr/local/mrourmon/bin
cp ombatch*.pl wormtolog.pl daily.pl monbackup.pl /usr/local/mrourmon/bin
cp omupdate.pl tcpworm.pl irc.pl /usr/local/mrourmon/bin
cp mklogdir.sh /usr/local/mrourmon/bin
chmod +x /usr/local/mrourmon/bin/*.sh
chmod +x /usr/local/mrourmon/bin/*.pl

INFO only: also setting up logging directory (if needed)
creating log rrddata tmp dirs, if necessary, in /usr/local/mrourmon
hit CR to continue:

If different, enter front-end output file directory absolute path: [/usr/local/mrourmon/tmp]
probe output file path (back-end input/s) is /usr/local/mrourmon/tmp

Now we copy supplied .html files to the web directory for later editing
do you want to copy base web files to the web directory? [y]

INFO only: setting up local rrdbase directory at /usr/local/mrourmon/rrddata
your runtime rrds get stored in this directory, along with the rrd error log file
if you create new BPF filters, check rrdbase/ourmon.log for errors.
hit CR to continue:

We need a UDP weight threshold for UDP scan alerts
what should the weight be (default is given): [10000000]

Install backend crontab commands in /etc/crontab (default answer y)?: [y]
y

ourmon system config complete
see INSTALL for post-config sanity checking

This is the error when I tried to start the ourmon.

[root@ /usr/local/etc/rc.d]# ./ourmon.sh start
sysctl: unknown oid 'debug.bpf_bufsize'
sysctl: unknown oid 'debug.bpf_maxbufsize'

When I opened the ourmon.sh, I found these lines under start_om():

sysctl -w debug.bpf_bufsize=8388608
sysctl -w debug.bpf_maxbufsize=8388608

In FreeBSD, they are called net.bpf.bufsize and net.bpf.maxbufsize. So just change them to these will do.

sysctl -w net.bpf.bufsize=8388608
sysctl -w net.bpf.maxbufsize=8388608

If you have your own value set in /etc/sysctl.conf, just comment these 2 lines.

I will post up as soon as Ourmon with threaded support is successfully setup on AMD64 system.