The supported Linux distribution in the School of Informatics, Computing, and Engineering is Red Hat Enterprise Linux per Supported Linux Configurations.  However, the school recognizes that certain projects will have dependencies on other Linux distributions and we make allowances for this per the IT Policy: Administrator Access and Self-Managed Systems.  This page is intended to provide guidance to administrators of Ubuntu-based self-manged systems so they remain in compliance with IU IT policies aimed at keeping system secure.  In some cases, instructions may be specific to a particular version of Ubuntu so you may have to make changes based on the version you are running.

  1. Identify Data Types - It is critical that you evaluate the types of data you will be storing, transmitting, or manipulating on your self-managed system.  If this involves any critical or restricted sensitive data, you MUST get prior approval before proceeding.  Please see Sensitive Data Policies and Email Encryption and let us know before proceeding if you will need to store, transmit, or manipulate any sensitive data.

  2. OS Version Selection - There are various versions of Ubuntu available and we strongly recommend selecting a Long-Term Support (LTS) version of Ubuntu.  This way your version of the OS will get security patches for as long a possible without having to make a major OS version upgrade.  You can run the ubuntu-support-status command to see the status of the system and end of support dates.

  3. Mobile Device Whole Disk Encryption - If you are installing Ubuntu on a laptop or other mobile device, you must use whole disk encryption to be in compliance with the Mobile Device Security Standard, Policy IT-12.1.  This is simple to do during the initial OS installation by just selecting the option.  For additional information see the Linux section of Mobile Device Security Standards.

  4. Manual Security Updates - You will want to set up automatic installation of security updates (per the next item below) but if you want to manually update your system you can see what updates are needed and update the system with:

    sudo /usr/lib/update-notifier/apt-check --human-readable
sudo apt-get update
sudo apt-get upgrade
sudo apt-get dist-upgrade

    See the apt-get man page for details on the various commands and exactly what they do.

  5. Automatic Security Updates- During the installation of Ubuntu, you will be asked if you want automated updates.  You must select the option to apply security updates automatically.  If you did not select this option during the initial installation, please enable it per the Ubuntu Automatic Updates Documentation.  You can run "sudo debconf-show unattended-upgrades" to see if the automatic updates are enabled and you can reconfigure it with "sudo dpkg-reconfigure -plow unattended-upgrades".  

    Once this is set up, you should see something like the following from debconf-show:

    $ sudo debconf-show unattended-upgrades
* unattended-upgrades/origins_pattern: "origin=Debian,codename=${distro_codename},label=Debian-Security";
* unattended-upgrades/enable_auto_updates: true


  6. Automatic Removal of Old Kernels - You will also want to configure things so that unused packages are automatically uninstalled.  If you don't do this then it is just a matter of time before your /boot partition fills up and which can cause various other problems.  One problem it will cause is that updates will then fail and your system will no longer get security updates automatically.  To enable the auto-removal of old kernel packages, edit the file /etc/apt/apt.conf.d/50unattended-upgrades and change these lines:

    //Unattended-Upgrade::Remove-Unused-Kernel-Packages "false";

//Unattended-Upgrade::Remove-Unused-Dependencies "false";

    to look like this (uncomment the lines and set to true)

    Unattended-Upgrade::Remove-Unused-Kernel-Packages "true";

Unattended-Upgrade::Remove-Unused-Dependencies "true";

    Note that the first line in this example may only be there for Ubuntu 18.04
    Reference: Ubuntu Community: Remove Old Kernels

  7. Account Passwords - To be in compliance with IU policy, all account passwords must comply with the IU Passphrase Guidelines, including the 15 character minimum length.  This includes the initial account you set up at install time and any other accounts you might add after the installation.  In addition, account passwords must be changed no less frequently than every 2 years to be in compliance with IU policy.  One good way to say in compliance with password guidelines is to set the system up so it uses the IU passphrase for account authentication.  This is simple to do by just installing these packages:

    sudo apt-get install heimdal-clients libpam-heimdal

    When promoted for the kerberos domain, enter "ADS.IU.EDU".

  8. Admin Access - Normal day-to-day usage of the system must be done using non-privileged (ie. non-root) accounts.  When elevated privileges are needed, sudo will be use.  This is the default mode of operation in Ubuntu so should not be a problem.  However, you are discouraged from routinely doing something like "sudo bash" to get a root shell when you can just run individual commands via sudo.

  9. Encryption Requirements - Any service that requires logins over the network must be encrypted.  So, for example, you must use ssh and sftp and not something like ftp that sends login information in cleartext.  This also includes web applications that require login access  so such sites must use https/SSL.

  10. Firewall Implementation - One of the most important security mechanisms is the implementation of a proper firewall.  In the linux world, that will likely be either iptables or firewalld.  With Ubuntu, UFW (Uncomplicated Firewall) is a popular frontend for managing iptables firewall rules.  There is a good guide to using UFW here:

    [Uncomplicated Firewall Ubuntu Wiki|https://wiki.ubuntu.com/UncomplicatedFirewall]

    An alternate method is to use iptables directly.  Here is a cookbook example of setting up iptables with Ubuntu 16.04 or 14.04 LTS:

    Step 1:  Set up the iptables rules.  In this example, we are opening up port 22 to the world for ssh.

    sudo iptables -A INPUT -m conntrack --ctstate ESTABLISHED,RELATED -j ACCEPT
    sudo iptables -A INPUT -p tcp --dport 22 -j ACCEPT
    sudo iptables -I INPUT 1 -i lo -j ACCEPT
    sudo iptables -A INPUT -p icmp --icmp-type echo-request -j ACCEPT
    sudo iptables -P INPUT DROP

    NOTE: This assumes the only port you want exposed on the network is port 22 (ssh).
          If you want additional ports open, add them like above for port 22.
          Just be sure to add them BEFORE the final DROP line.
          See the next step for additional notes about opening up port 22.

Step 2: Install iptables-persistent to manage things and save the config

     sudo apt-get update
     sudo apt-get install iptables-persistent

     NOTE: Rules will be saved to /etc/iptables/rules.v4 during install

Step 3: If you make any further changes to the rules, save them out with:

     14.04:  sudo /etc/init.d/iptables-persistent save
     16.04:  sudo netfilter-persistent save
     18.04:  sudo netfilter-persistent save

 Example:  Here is an example of how to add a new rule and save it out after iptables is already set up on 16.04:

   # Open up port 1234 by inserting the rule into the chain
   sudo iptables -I INPUT 3 -p tcp --dport 1234 -j ACCEPT

   # If you wanted to open up port 1234 to only the host with IP address 1.2.3.4 you could do that with:
   sudo iptables -I INPUT 3 -s 1.2.3.4 -p tcp --dport 1234 -j ACCEPT

   # Verify that the rule looks good and is in the right place
   sudo iptables -v -L --line-numbers

   # Save it out
   sudo netfilter-persistent save

Example:  Here is an example of how to remove an existing rule and save it out after iptables is already set up on 16.04 or 18.04:

   # View the current rules, with line numbers
   sudo iptables -v -L --line-numbers

   # Identify the rule you want to remove and note the line number.  Remove that line by number
   sudo iptables -D INPUT N
        Note:  Replace 'N' with the line number of the rule to remove

   # Verify that the rules looks good and the rule has been removed
   sudo iptables -v -L --line-numbers

   # Save it out
   sudo netfilter-persistent save


  11. Block Brute-Force SSH Attacks - If you have opened port 22 for ssh logins to the world in the firewall then you must take action to prevent brute-force login attempts.  One simple way to do this is using Fail2ban.  Here are a couple good references on how to set it up:

    1. How to install Fail2ban on Ubuntu
    2. How To Protect SSH and Apache Using Fail2Ban on Ubuntu Linux


    Alternately, you could restrict access to a more limited set of IP subnets in the firewall rules.  For example, you could replace the above iptables rule that opens ssh to the world to include only the primary IU subnets by replacing the above rule:

        sudo iptables -A INPUT -p tcp --dport 22 -j ACCEPT

    with the following set of rules that limit access to all the IU subnets:

        sudo iptables -A INPUT -p tcp -s 129.79.0.0/16 --dport 22 -j ACCEPT
    sudo iptables -A INPUT -p tcp -s 156.56.0.0/16 --dport 22 -j ACCEPT
    sudo iptables -A INPUT -p tcp -s 140.182.0.0/16 --dport 22 -j ACCEPT
    sudo iptables -A INPUT -p tcp -s 149.159.0.0/16 --dport 22 -j ACCEPT
    sudo iptables -A INPUT -p tcp -s 149.160.0.0/16 --dport 22 -j ACCEPT
    sudo iptables -A INPUT -p tcp -s 149.161.0.0/16 --dport 22 -j ACCEPT
    sudo iptables -A INPUT -p tcp -s 149.165.0.0/16 --dport 22 -j ACCEPT



  12. Disable Guest Account - There may be a guest account created by default so you should disable that per How do I disable the guest session?
  13. Disable Remote Root SSH Logins - You want to be sure that root logins are not allowed via remote ssh connections.  You can ensure this is the case by making sure you have the line PermitRootLogin no  in the sshd config files (/etc/ssh/sshd_config).

  14. Remove or Disable mDNS/avahi-daemon - You should ensure that avahi-daemon is not running and providing mDNS services.  This is almost certainly not needed on the IU network and can leave the system open to abuse.  You can just remove the avahi-daemon package entirely (preferred) or disable it as follows:

    Preferred: Remove the service

    sudo apt-get remove avahi-daemon

Alternate: Disable and stop the service

     echo manual | sudo tee /etc/init/avahi-daemon.override
     sudo stop avahi-daemon


  15. Securing Services - You may need to run a variety of services on the system, including web and database servers.  It is recommended that you limit networked services as much as possible and use IU and SICE servers if at all possible.  Furthermore, if you do run such services it is best to limit their exposure on the network if they are only needed locally on the system.  For example, a database server (like mysqld or mongod) that is used by a web server running on the same system need not be exposed on the network.  We can't list every single service you may need to run but do have some specific recommendations for some common services in use within the school:

  16. System Logging - IU has specific logging requirements for all servers operating on the IU network per IT Policy IT-12.  If your Ubuntu system is operating as a server on the IU network (eg. web, database, etc), you need to set up logging as follows:

    1. Auditd - You must set up auditd as described at Configuring and auditing Linux systems with Audit daemon.  There is also information in the IU KB page INTERNAL (iu-kb): About Splunk audit configurations (you must log in to view this page).  You can install this on Ubuntu with:

      sudo apt-get install auditd audispd-plugins


      Here is a minimal /etc/audit/audit.rules file that meets IT-12 requirements on a system with no sensitive data:

      -D
-b 320
-a exit,always -F arch=b64 -S open -F exit=-EACCES
-a exit,always -F arch=b64 -S open -F exit=-EPERM
-a exit,always -F arch=b32 -S open -F exit=-EACCES
-a exit,always -F arch=b32 -S open -F exit=-EPERM

      This will log all failed file access attempts as well as both failed and successful logins.  On a system with sensitive data, you must also log all successful file accesses.  For example, if you were storing sensitive data in /home/goodies then you would add the following to the above auditd rules:

      -w /home/goodies -p wrxa

      Once you have the audit.rules file configured, you can restart auditd and verify by running:

      sudo /etc/init.d/auditd restart
sudo auditctl -l

      Please let us know if you need any help setting this up.

    2. Splunkforwarder - The auditd data should be forwarded to the IU Log-Alert service using Splunkforwarder.  This prevents possible tampering with the data that resides local to the system.  The installation is done via an installer script that we can provide  Please let us know and we can provide the installer script and packages.

  17. Account Maintenance - You will need to review all user accounts on the system monthly and purge any accounts that are no longer needed.

  18. VMware Tools Installation - If you are setting up a Ubuntu VM in the IU Intelligent Infrastructure (II) system you must install VMware tools.  We recommend you use the open VMware tools as follows:

    sudo apt-get install open-vm-tools


  19. OS Patch Maintenance - As noted above, you are required to configure the system so that security updates are installed automatically.  However, you are encouraged to install other maintenance updates on a regular schedule.

  20. Security Vulnerability Scans - All systems on the SICE networks will be automatically scanned using an external security scanner monthly.  We will contact you to resolve any vulnerabilities that show up for your system and we expect that you will work promptly to resolve all reported issues.

  21. Breach Reporting - In the event of a security breach, it must be reported immediately per IT Policy: Incident Response 

If you have any questions about this or need further assistance, please contact us via the help desk.