Guide to the Secure Configuration of Ubuntu 16.04
Rules, Groups, and Values defined within the XCCDF Benchmark
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Configure NFS Clients
The steps in this section are appropriate for systems which operate as NFS clients.Group -
Disable NFS Server Daemons
There is no need to run the NFS server daemons <code>nfs</code> and <code>rpcsvcgssd</code> except on a small number of properly secured systems de...Group -
Mount Remote Filesystems with Restrictive Options
Edit the file <code>/etc/fstab</code>. For each filesystem whose type (column 3) is <code>nfs</code> or <code>nfs4</code>, add the text <code>,node...Group -
Configure NFS Servers
The steps in this section are appropriate for systems which operate as NFS servers.Group -
Ensure All-Squashing Disabled On All Exports
The <code>all_squash</code> maps all uids and gids to an anonymous user. This should be disabled by removing any instances of the <code>all_squash<...Rule Low Severity -
Configure the Exports File Restrictively
Linux's NFS implementation uses the file <code>/etc/exports</code> to control what filesystems and directories may be accessed via NFS. (See the <c...Group -
Export Filesystems Read-Only if Possible
If a filesystem is being exported so that users can view the files in a convenient fashion, but there is no need for users to edit those files, exp...Group -
Use Access Lists to Enforce Authorization Restrictions
When configuring NFS exports, ensure that each export line in <code>/etc/exports</code> contains a list of hosts which are allowed to access that e...Group -
Network Time Protocol
The Network Time Protocol is used to manage the system clock over a network. Computer clocks are not very accurate, so time will drift unpredictabl...Group -
Vendor Approved Time pools
The list of vendor-approved pool serversValue -
Vendor Approved Time Servers
The list of vendor-approved time serversValue -
Maximum NTP or Chrony Poll
The maximum NTP or Chrony poll interval number in seconds specified as a power of two.Value -
The Chrony package is installed
System time should be synchronized between all systems in an environment. This is typically done by establishing an authoritative time server or se...Rule Medium Severity -
Install the ntp service
The ntpd service should be installed.Rule High Severity -
The Chronyd service is enabled
chrony is a daemon which implements the Network Time Protocol (NTP) is designed to synchronize system clocks across a variety of systems and use a ...Rule Medium Severity -
Enable the NTP Daemon
Thentp
service can be enabled with the following command:$ sudo systemctl enable ntp.service
Rule High Severity -
Enable systemd_timesyncd Service
Thesystemd_timesyncd
service can be enabled with the following command:$ sudo systemctl enable systemd_timesyncd.service
Rule High Severity -
Ensure Chrony is only configured with the server directive
Check that Chrony only has time sources configured with theserver
directive.Rule Medium Severity -
A remote time server for Chrony is configured
<code>Chrony</code> is a daemon which implements the Network Time Protocol (NTP). It is designed to synchronize system clocks across a variety of s...Rule Medium Severity -
Obsolete Services
This section discusses a number of network-visible services which have historically caused problems for system security, and for which disabling or...Group
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