Email Configuration

so-email

If you want to configure email, you can run so-email and it will automatically configure automated server-side email for you as described below. Simply run the following command and follow the prompts:

sudo so-email

To automate email setup, copy and modify the example file located at /usr/share/securityonion/so-email.conf, then run so-email with the -f flag:

sudo so-email -f ~/so-email.conf

Sguil client

Please note that the Sguil client has its own email configuration (separate from the Sguil server) which can be modified in /etc/sguil/sguil.conf.

Manual Configuration

If you don’t want to run so-email as described above, you can configure email manually as described in the following sections. Applications such as Sguil and Wazuh have their own mail configuration and don’t rely on a mail server in the OS itself. However, you may still want to install a mail server in the OS so that you can get daily emails from the sostat script and from Bro.

Operating System

Install and configure your favorite mail server. Depending on your needs, this could be something simple like nullmailer (recommended) or something more complex like exim4.

Here are some nullmailer instructions provided by Michael Iverson:

sudo apt-get install nullmailer

# edit /etc/mailname to hold your "from" domain name. (If you were google, you'd use "gmail.com".)

# edit /etc/nullmailer/adminaddr to contain the address you want mail to root to be routed to.

# edit /etc/nullmailer/remotes to contain the mail server to forward email to.

Alternatively, here are some instructions for the more complex exim4:

sudo apt-get -y install mailutils
sudo dpkg-reconfigure exim4-config

Once you’ve configured your mail server and verified that it can send email properly, you might want to create a daily cronjob to execute /usr/sbin/sostat and email you the output:

# /etc/cron.d/sostat
crontab entry to run sostat and email its output
------------------------------------------------
SHELL=/bin/sh
PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin
EMAIL=YourUsername@YourDomain.com\
01 12 * * * root HOSTNAME=$(hostname); /usr/sbin/sostat 2>&1 | mail -s "$HOSTNAME stats" $EMAIL

If you don’t already have the mail utility, you can try installing:

sudo apt-get install mailutils

Sguild

Modify /etc/nsm/securityonion/sguild.email (on the master server) as needed and restart sguild:

sudo so-sguild-restart

You can then verify the email configuration by looking at the top of sguild’s log file:

head -20 /var/log/nsm/securityonion/sguild.log

For more information, please see http://nsmwiki.org/Sguil_FAQ#Can_sguil_page_me_when_it_sees_a_particular_alert.3F.

You may want to install a local mail relay on your master server, configure it to relay mail to your corporate mail server, and then configure Sguil to send email to the local mail relay.

Please note: Sguil will only send email alerts for what is considers new events. Ensure you classify events within the Sguil console, or consider creating an Autocat rule to automatically classify them if you prefer to receive emails for all instances of an alert. Otherwise, you may not receive alerts as intended.

Wazuh

Modify /var/ossec/etc/ossec.conf as follows:

<global>
<email_notification>yes</email_notification>
<email_to>YourUsername@YourDomain.com</email_to>
<smtp_server>YourMailRelay.YourDomain.com</smtp_server>
<email_from>ossec@YourDomain.com</email_from>
<email_maxperhour>100</email_maxperhour>
</global>

Then restart Wazuh:

sudo so-ossec-restart

You can specify the severity of an event for which Wazuh will send email alerts by specifying an appropriate value for email_alert_level in /var/ossec/etc/ossec.conf. If you notice email_alert_level is not being respected for a certain rule, it may be that the option is overridden by <options>alert_by_email</options> being set for a rule. You can modify this behavior in /var/ossec/rules/local.rules.

You can also find an explanation of the alert levels at http://ossec-docs.readthedocs.io/en/latest/manual/rules-decoders/rule-levels.html.

Bro

Edit /opt/bro/etc/broctl.cfg and set the following:

MailTo = YourUsername@YourDomain.com
sendmail = /usr/sbin/sendmail

Then update and restart Bro:

sudo so-bro-restart

You should then start receiving hourly connection summary emails. If you don’t want the connection summary emails, you can add the following to broctl.cfg and update and restart Bro as shown above:

tracesummary=

You may want to receive emails for Bro notices. To do that, add the following to /opt/bro/share/bro/site/local.bro and update/restart Bro as shown above:

hook Notice::policy(n: Notice::Info)
{
add n$actions[Notice::ACTION\_ALARM];
}

Also see http://mailman.icsi.berkeley.edu/pipermail/bro/2013-December/006418.html.

Elastalert

Follow the steps on the Elastalert page.

Lack of network traffic

If you configured Wazuh or Bro as shown above, they should automatically email you if your network sensors stop seeing traffic.