Security Onion

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Security Onion is a Linux distro for IDS (Intrusion Detection) and NSM (Network Security Monitoring). It's based on Ubuntu and contains Snort, Suricata, Sguil, Squert, Snorby, Bro, NetworkMiner, Xplico, and many other security tools. The easy-to-use Setup wizard allows you to build an army of distributed sensors for your enterprise in minutes!


Disable an SID (alert)

Security Onion uses PulledPork (a perl script maintained by JJ Cummings) that downloads new signatures every night and processes them against a set list of user generated configurations.

In a Server/Slave Security Onion environment, you only need to change the configuration file on the server and the rule-update script will sync with the signatures from the Server. As mentioned before, take care in disabling signatures as it can be likely that a more appropriate response is warranted.

  • Edit the disablesid.conf configuration file:
sudo vi /etc/nsm/pulledpork/disablesid.conf  #Security Onion 12.04
sudo vi /etc/pulledpork/disablesid.conf      #Security Onion 10.04
You can also access the disablesid.conf file by clicking Applications->IDS Rules->Disable Downloaded Rules. You will need to provide your password.

  • Append the signature you wish to disable in the format gid:sid. The generator ID is most likely going to be a "1" in most cases. You can check the generator ID by checking the exact signature. If a gid is not listed, it is assumed to be "1".
     # Disable the GPL SNMP public access udp signature

  • Run the rule update on the server:
     sudo /usr/bin/rule-update                #Security Onion 12.04
     sudo /usr/local/bin/ #Security Onion 10.04

  • Run the rule update on the slave machines:
     sudo /usr/bin/rule-update                #Security Onion 12.04
     sudo /usr/local/bin/ #Security Onion 10.04

Suppress SID

  • this is usefull to disable alerts based on src_ip,dst_ip. Otherwise, I'd suggest to disable the rule entirely

SecurityOnion 12.04 based version use /etc/nsm/rules/threshold.conf):

suppress gen_id 1, sig_id 2101411, track by_src, ip
  • Once the correct suppression has been placed in threshold.conf, restart the alert engine:
sudo nsm_sensor_ps-restart --only-snort-alert
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