Saturday, April 25, 2015

Suricata - check loaded yaml config settings with --dump-config

There is a very useful command available to Suricata IDS/IPS/NSM :
suricata --dump-config

The command above will dump all the config parameters and their respective values that are loaded by Suricata from the config file. You can run the command in any case - it does not matter if Suricata is running or not.

There is a peculiarity however. Sometimes people would think that the command(above) would dump the currently loaded config values by Suricata.... in some case it will and in some cases it will not.

So what does it depend on?.... simple:
suricata --dump-config

will dump the config settings that are loaded (or will be loaded) by Suricata by default from

So if you are running Suricata with a config file called suricata-test.yaml (or suricata.yaml located in a different directory) - you will not see those settings...unless you specify that config file in particular:
suricata --dump-config -c /etc/suricata/suricata-test.yaml
Here is a real case example.
I run Suricata for a specific test where I had specified the defrag memcap to be 512mb :
  memcap: 512mb
  hash-size: 65536
  trackers: 65535 # number of defragmented flows to follow
  max-frags: 65535 # number of fragments to keep (higher than trackers)
  prealloc: yes
  timeout: 60

Suricata up and running:
root@LTS-64-1:~/Work # ps aux |grep suricata
root      8109  2.3  7.6 878444 308372 pts/6   Sl+  12:45   1:02 suricata -c /etc/suricata/suricata-test.yaml --af-packet=eth0 -v
root@LTS-64-1:~/Work #

And the peculiarity that this blogpost is trying to emphasize on about :
root@LTS-64-1:~/Work # suricata --dump-config  |grep defrag.memcap
defrag.memcap = 32mb
root@LTS-64-1:~/Work # suricata --dump-config -c /etc/suricata/suricata-test.yaml |grep defrag.memcap
defrag.memcap = 512mb
root@LTS-64-1:~/Work #

suricata --dump-config dumps the settings loaded(or to be loaded) from the default location /etc/suricata/suricata.yaml if you are running suricata with a yaml config with a different name than the default or with a different location that the default - in order to get those settings - you need to specify that particular yaml location, like so:

suricata --dump-config -c /etc/local/some_test_dir/suricata/suricata-test.yaml


related article:

Monday, April 6, 2015

Suricata IDPS - Application layer anomalies protocol detection

Suricata IDS/IPS/NSM also allows you to do application layer anomaly  detection.
I started talking to inliniac about protocol anomaly detection rules one day on the Suricata IRC chat room...which evolved more into a discussion resulting in us updating the rule sets with some examples of how to do that.

Below are a few examples for rules usage:


alert tcp any any -> any ![80,8080] (msg:"SURICATA HTTP not tcp port 80, 8080"; flow:to_server; app-layer-protocol:http; sid:2271001; rev:1;)
The above rule finds http traffic that is not using dest port 80 or 8080.

alert tcp any any -> any 80 (msg:"SURICATA Port 80 but not HTTP"; flow:to_server; app-layer-protocol:!http; sid:2271002; rev:1;)
The above rule is kind of the reverse of the previous one - it will alert if the tcp traffic with destination port 80 is not http.

Here is another example


alert tcp any any -> any 443 (msg:"SURICATA Port 443 but not TLS"; flow:to_server; app-layer-protocol:!tls; sid:2271003; rev:1;)


Detecting HTTP traffic over HTTPS port -

alert http any any -> any 443 (msg:"SURICATA HTTP clear text on port 443"; flow:to_server; app-layer-protocol:http; sid:2271019; rev:1;)

You can find the full ruleset (open source and free to use) with examples for HTTP, HTTPS, TLS, FTP, SMTP, SSH, IMAP, SMB, DCERPC, DNS, MODBUS application layer anomaly  detection  here: