[Oisf-users] Create a suricata pass rule for Nagios check_http

Claudio Kuenzler ck at claudiokuenzler.com
Mon Mar 2 14:09:31 UTC 2015

Hello all,

I'm trying to add my own rule so Nagios' check_http plugin are not creating
alerts when coming from my fixed Nagios server.

Currently the following alerts are logged (in fast.log):

03/02/2015-15:00:27.043197  [**] [1:2013030:3] ET POLICY libwww-perl
User-Agent [**] [Classification: Attempted Information Leak] [Priority: 2]
{TCP} ->

Where is the destination server I'm monitoring. The SID responsible
for this alert is the following:

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET POLICY libwww-perl
User-Agent"; flow:established,to_server; content:"User-Agent|3a|
libwww-perl/"; nocase; http_header; reference:url,
classtype:attempted-recon; sid:2013030; rev:3;)

The alert itself is ok, but I don't want to get alerts when this alert is
triggered from my monitoring server. Therefore I created my own rule which
hopefully would tell suricata to not alert when coming from my monitoring
server. As of now I didn't add "pass" as the action but "alert" to see if
the rule is being fired:

alert any any -> $EXTERNAL_NET any (msg:"Monitoring Check";
flow:established,to_server; priority:1; sid:444888001; rev:3;)

Unfortunately nothing happens. SID 2013030 is still being fired when my
monitoring server runs the check_http.

The new rules file was added into suricata.yaml and it is being read. I
made a typo at the begin and this error was logged in suricata.log when I
restarted suricata.
And yes, suricata was restarted.

Did I miss something? Did I make a mistake in the rule?
Is it even possible to overwrite an existing SID the way I want?

That's my first manual rule I'm trying to add, so have patience with me ;-)
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