How to use lynis for linux vulnerability scanning

2020-10-23 20:23:50
OfStack

preface

lynis is a host-based, open source security audit software running on the Unix/Linux platform. Lynis is a security check tool for Unix/Linux that can detect potential security threats. This tool covers suspect file monitoring, vulnerabilities, malicious program scanning, configuration errors, and more. Take a look at using lynis for linux vulnerability scanning

Install lynis

On archlinux you can install directly via pacman


sudo pacman -S lynis --noconfirm


resolving dependencies...
looking for conflicting packages...
 
Packages (1) lynis-2.6.4-1
 
Total Installed Size: 1.35 MiB
Net Upgrade Size:  0.00 MiB
 
:: Proceed with installation? [Y/n] 
(0/1) checking keys in keyring      [----------------------] 0%
(1/1) checking keys in keyring      [######################] 100%
(0/1) checking package integrity     [----------------------] 0%
(1/1) checking package integrity     [######################] 100%
(0/1) loading package files      [----------------------] 0%
(1/1) loading package files      [######################] 100%
(0/1) checking for file conflicts     [----------------------] 0%
(1/1) checking for file conflicts     [######################] 100%
(0/1) checking available disk space    [----------------------] 0%
(1/1) checking available disk space    [######################] 100%
:: Processing package changes...
(1/1) reinstalling lynis       [----------------------] 0%
(1/1) reinstalling lynis       [######################] 100%
:: Running post-transaction hooks...
(1/2) Reloading system manager configuration...
(2/2) Arming ConditionNeedsUpdate...

Use lynis for host scanning

First, let's run lynis without any arguments, which will list those supported by lynis


[lujun9972@T520 linux And his little friend ]$ lynis
 
[ Lynis 2.6.4 ]
 
################################################################################
 Lynis comes with ABSOLUTELY NO WARRANTY. This is free software, and you are
 welcome to redistribute it under the terms of the GNU General Public License.
 See the LICENSE file for details about using this software.
 
 2007-2018, CISOfy - https://cisofy.com/lynis/
 Enterprise support available (compliance, plugins, interface and tools)
################################################################################
 
 
[+] Initializing program
------------------------------------
 
 
 Usage: lynis command [options]
 
 
 Command:
 
 audit
  audit system     : Perform local security scan
  audit system remote <host> : Remote security scan
  audit dockerfile <file>  : Analyze Dockerfile
 
 show
  show       : Show all commands
  show version     : Show Lynis version
  show help      : Show help
 
 update
  update info     : Show update details
 
 
 Options:
 
 --no-log       : Don't create a log file
 --pentest       : Non-privileged scan (useful for pentest)
 --profile <profile>    : Scan the system with the given profile file
 --quick (-Q)      : Quick mode, don't wait for user input
 
 Layout options
 --no-colors      : Don't use colors in output
 --quiet (-q)      : No output
 --reverse-colors     : Optimize color display for light backgrounds
 
 Misc options
 --debug       : Debug logging to screen
 --view-manpage (--man)   : View man page
 --verbose       : Show more details on screen
 --version (-V)     : Display version number and quit
 
 Enterprise options
 --plugindir <path>    : Define path of available plugins
 --upload       : Upload data to central node
 
 More options available. Run '/usr/bin/lynis show options', or use the man page.
 
 No command provided. Exiting..

As you can see from the above, using lynis for host scanning is very simple. You only need to take the parameter audit system. Lynis performs a variety of similar tests during the audit, during which various test results, debugging information, and reinforcement recommendations for the system are written to stdin. We can skip the inspection process by executing the following command and directly intercept the final scan recommendation.


sudo lynis audit system |sed '1,/Results/d'

lynis divides the scanned content into several categories, which can be obtained by using the show groups parameter


lynis show groups

[

accounting
authentication
banners
boot_services
containers
crypto
databases
dns
file_integrity
file_permissions
filesystems
firewalls
hardening
homedirs
insecure_services
kernel
kernel_hardening
ldap
logging
mac_frameworks
mail_messaging
malware
memory_processes
nameservices
networking
php
ports_packages
printers_spools
scheduling
shells
snmp
squid
ssh
storage
storage_nfs
system_integrity
time
tooling
usb
virtualization
webservers

]

The tests-ES131en-ES132en parameter can be used to specify if it points to a scan of some class of content.

For example, if I just want to scan shells and networking, I can do it


sudo lynis --tests-from-group "shells networking" --no-colors


[ Lynis 2.6.4 ]
 
################################################################################
 Lynis comes with ABSOLUTELY NO WARRANTY. This is free software, and you are
 welcome to redistribute it under the terms of the GNU General Public License.
 See the LICENSE file for details about using this software.
 
 2007-2018, CISOfy - https://cisofy.com/lynis/
 Enterprise support available (compliance, plugins, interface and tools)
################################################################################
 
 
[+] Initializing program
------------------------------------
[2C- Detecting OS... [41C [ DONE ]
[2C- Checking profiles...[37C [ DONE ]
[2C- Detecting language and localization[22C [ zh ]
[4CNotice: no language file found for 'zh' (tried: /usr/share/lynis/db/languages/zh)[0C
 
 ---------------------------------------------------
 Program version:   2.6.4
 Operating system:   Linux
 Operating system name:  Arch Linux
 Operating system version: Rolling release
 Kernel version:   4.16.13
 Hardware platform:   x86_64
 Hostname:     T520
 ---------------------------------------------------
 Profiles:     /etc/lynis/default.prf
 Log file:     /var/log/lynis.log
 Report file:    /var/log/lynis-report.dat
 Report version:   1.0
 Plugin directory:   /usr/share/lynis/plugins
 ---------------------------------------------------
 Auditor:     [Not Specified]
 Language:     zh
 Test category:    all
 Test group:    shells networking
 ---------------------------------------------------
[2C- Program update status... [32C [ NO UPDATE ]
 
[+] System Tools
------------------------------------
[2C- Scanning available tools...[30C
[2C- Checking system binaries...[30C
 
[+] Plugins (phase 1)
------------------------------------
[0CNote: plugins have more extensive tests and may take several minutes to complete[0C
[0C [0C
[2C- Plugins enabled[42C [ NONE ]
 
[+] Shells
------------------------------------
[2C- Checking shells from /etc/shells[25C
[4CResult: found 5 shells (valid shells: 5).[16C
[4C- Session timeout settings/tools[25C [ NONE ]
[2C- Checking default umask values[28C
[4C- Checking default umask in /etc/bash.bashrc[13C [ NONE ]
[4C- Checking default umask in /etc/profile[17C [ WEAK ]
 
[+] Networking
------------------------------------
[2C- Checking IPv6 configuration[30C [ ENABLED ]
[6CConfiguration method[35C [ AUTO ]
[6CIPv6 only[46C [ NO ]
[2C- Checking configured nameservers[26C
[4C- Testing nameservers[36C
[6CNameserver: 202.96.134.33[30C [ SKIPPED ]
[6CNameserver: 202.96.128.86[30C [ SKIPPED ]
[4C- Minimal of 2 responsive nameservers[20C [ SKIPPED ]
[2C- Getting listening ports (TCP/UDP)[24C [ DONE ]
[6C* Found 11 ports[39C
[2C- Checking status DHCP client[30C [ RUNNING ]
[2C- Checking for ARP monitoring software[21C [ NOT FOUND ]
 
[+] Custom Tests
------------------------------------
[2C- Running custom tests... [33C [ NONE ]
 
[+] Plugins (phase 2)
------------------------------------
 
================================================================================
 
 -[ Lynis 2.6.4 Results ]-
 
 Great, no warnings
 
 Suggestions (1):
 ----------------------------
 * Consider running ARP monitoring software (arpwatch,arpon) [NETW-3032] 
 
https://cisofy.com/controls/NETW-3032/
 
 Follow-up:
 ----------------------------
 - Show details of a test (lynis show details TEST-ID)
 - Check the logfile for all details (less /var/log/lynis.log)
 - Read security controls texts (https://cisofy.com)
 - Use --upload to upload data to central system (Lynis Enterprise users)
 
================================================================================
 
 Lynis security scan details:
 
 Hardening index : 33 [######    ]
 Tests performed : 13
 Plugins enabled : 0
 
 Components:
 - Firewall    [X]
 - Malware scanner  [X]
 
 Lynis Modules:
 - Compliance Status  [?]
 - Security Audit   [V]
 - Vulnerability Scan  [V]
 
 Files:
 - Test and debug information  : /var/log/lynis.log
 - Report data      : /var/log/lynis-report.dat
 
================================================================================
 
 Lynis 2.6.4
 
 Auditing, system hardening, and compliance for UNIX-based systems
 (Linux, macOS, BSD, and others)
 
 2007-2018, CISOfy - https://cisofy.com/lynis/
 Enterprise support available (compliance, plugins, interface and tools)
 
================================================================================
 
 [TIP]: Enhance Lynis audits by adding your settings to custom.prf (see /etc/lynis/default.prf for all settings)

View details

When viewing the audit results, you can use the show details parameter to get a detailed description of a particular warning/recommendation. Its corresponding command form is:


lynis show details ${test_id}

For example, there is one suggestion in the figure above


* Consider running ARP monitoring software (arpwatch,arpon) [NETW-3032]

We can run the command:


sudo lynis show details NETW-3032


resolving dependencies...
looking for conflicting packages...
 
Packages (1) lynis-2.6.4-1
 
Total Installed Size: 1.35 MiB
Net Upgrade Size:  0.00 MiB
 
:: Proceed with installation? [Y/n] 
(0/1) checking keys in keyring      [----------------------] 0%
(1/1) checking keys in keyring      [######################] 100%
(0/1) checking package integrity     [----------------------] 0%
(1/1) checking package integrity     [######################] 100%
(0/1) loading package files      [----------------------] 0%
(1/1) loading package files      [######################] 100%
(0/1) checking for file conflicts     [----------------------] 0%
(1/1) checking for file conflicts     [######################] 100%
(0/1) checking available disk space    [----------------------] 0%
(1/1) checking available disk space    [######################] 100%
:: Processing package changes...
(1/1) reinstalling lynis       [----------------------] 0%
(1/1) reinstalling lynis       [######################] 100%
:: Running post-transaction hooks...
(1/2) Reloading system manager configuration...
(2/2) Arming ConditionNeedsUpdate...

View log files

lynis after completion of the audit will be detailed information recorded on/var log/lynis log.


resolving dependencies...
looking for conflicting packages...
 
Packages (1) lynis-2.6.4-1
 
Total Installed Size: 1.35 MiB
Net Upgrade Size:  0.00 MiB
 
:: Proceed with installation? [Y/n] 
(0/1) checking keys in keyring      [----------------------] 0%
(1/1) checking keys in keyring      [######################] 100%
(0/1) checking package integrity     [----------------------] 0%
(1/1) checking package integrity     [######################] 100%
(0/1) loading package files      [----------------------] 0%
(1/1) loading package files      [######################] 100%
(0/1) checking for file conflicts     [----------------------] 0%
(1/1) checking for file conflicts     [######################] 100%
(0/1) checking available disk space    [----------------------] 0%
(1/1) checking available disk space    [######################] 100%
:: Processing package changes...
(1/1) reinstalling lynis       [----------------------] 0%
(1/1) reinstalling lynis       [######################] 100%
:: Running post-transaction hooks...
(1/2) Reloading system manager configuration...
(2/2) Arming ConditionNeedsUpdate...


resolving dependencies...
looking for conflicting packages...
 
Packages (1) lynis-2.6.4-1
 
Total Installed Size: 1.35 MiB
Net Upgrade Size:  0.00 MiB
 
:: Proceed with installation? [Y/n] 
(0/1) checking keys in keyring      [----------------------] 0%
(1/1) checking keys in keyring      [######################] 100%
(0/1) checking package integrity     [----------------------] 0%
(1/1) checking package integrity     [######################] 100%
(0/1) loading package files      [----------------------] 0%
(1/1) loading package files      [######################] 100%
(0/1) checking for file conflicts     [----------------------] 0%
(1/1) checking for file conflicts     [######################] 100%
(0/1) checking available disk space    [----------------------] 0%
(1/1) checking available disk space    [######################] 100%
:: Processing package changes...
(1/1) reinstalling lynis       [----------------------] 0%
(1/1) reinstalling lynis       [######################] 100%
:: Running post-transaction hooks...
(1/2) Reloading system manager configuration...
(2/2) Arming ConditionNeedsUpdate...

Meanwhile, the report data is saved in /var/log/ ES168en-ES169en.dat.


sudo tail /var/log/lynis-report.dat

It is also important to note that the original log file is overwritten with each audit.

Check the update

The audit software needs to be updated at any time to get the latest advice and information. We can use the update info parameter to check for updates:


resolving dependencies...
looking for conflicting packages...
 
Packages (1) lynis-2.6.4-1
 
Total Installed Size: 1.35 MiB
Net Upgrade Size:  0.00 MiB
 
:: Proceed with installation? [Y/n] 
(0/1) checking keys in keyring      [----------------------] 0%
(1/1) checking keys in keyring      [######################] 100%
(0/1) checking package integrity     [----------------------] 0%
(1/1) checking package integrity     [######################] 100%
(0/1) loading package files      [----------------------] 0%
(1/1) loading package files      [######################] 100%
(0/1) checking for file conflicts     [----------------------] 0%
(1/1) checking for file conflicts     [######################] 100%
(0/1) checking available disk space    [----------------------] 0%
(1/1) checking available disk space    [######################] 100%
:: Processing package changes...
(1/1) reinstalling lynis       [----------------------] 0%
(1/1) reinstalling lynis       [######################] 100%
:: Running post-transaction hooks...
(1/2) Reloading system manager configuration...
(2/2) Arming ConditionNeedsUpdate...


resolving dependencies...
looking for conflicting packages...
 
Packages (1) lynis-2.6.4-1
 
Total Installed Size: 1.35 MiB
Net Upgrade Size:  0.00 MiB
 
:: Proceed with installation? [Y/n] 
(0/1) checking keys in keyring      [----------------------] 0%
(1/1) checking keys in keyring      [######################] 100%
(0/1) checking package integrity     [----------------------] 0%
(1/1) checking package integrity     [######################] 100%
(0/1) loading package files      [----------------------] 0%
(1/1) loading package files      [######################] 100%
(0/1) checking for file conflicts     [----------------------] 0%
(1/1) checking for file conflicts     [######################] 100%
(0/1) checking available disk space    [----------------------] 0%
(1/1) checking available disk space    [######################] 100%
:: Processing package changes...
(1/1) reinstalling lynis       [----------------------] 0%
(1/1) reinstalling lynis       [######################] 100%
:: Running post-transaction hooks...
(1/2) Reloading system manager configuration...
(2/2) Arming ConditionNeedsUpdate...

Custom lynis security audit policy

The configuration information for lynis is saved in the /etc/lynis directory as a.prf file. The default lynis comes with a default configuration file named ES192en.prf.

Instead of modifying the default configuration file, we simply added an custom.prf file to add custom information.

The meaning of each configuration item in the configuration file is explained in default.prf, which I will not elaborate on here.

To learn more about lynis, visit its website.

conclusion