As a system administrator, Linux security technician or system auditor, your responsibility can involve any combination of these: software patch management, malware scanning, file integrity checks, security audit, configuration error checking, etc. If there is an automatic vulnerability scanning tool, it can save you a lot of time checking up on common security issues.
One such vulnerability scanner on Linux is lynis. This tool is actually supported on multiple platforms including CentOS, Debian, Fedora, FreeBSD, Mac OS and Ubuntu.
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To install lynis on Linux, do the following.
$ wget http://www.rootkit.nl/files/lynis-1.3.0.tar.gz
$ sudo tar xvfvz lynis-1.3.0.tar.gz -C /opt
To scan Linux for vulnerabilities with lynis, run the following.
$ cd /opt/lynis-1.3.0/
$ sudo ./lynis --check-all -Q
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Once lynis starts scanning your system, it will perform auditing in a number of categories:
System tools: system binaries
Boot and services: boot loaders, startup services
Kernel: run level, loaded modules, kernel configuration, core dumps
Memory and processes: zombie processes, IO waiting processes
Users, groups and authentication: group IDs, sudoers, PAM configuration, password aging, default mask
Shells
File systems: mount points, /tmp files, root file system
Storage: usb-storage, firewire ohci
NFS
Software: name services: DNS search domain, BIND
Ports and packages: vulnerable/upgradable packages, security repository
Networking: nameservers, promiscuous interfaces, connections
Printers and spools: cups configuration
Software: e-mail and messaging
Software: firewalls: iptables, pf
Software: webserver: Apache, nginx
SSH support: SSH configuration
SNMP support
Databases: MySQL root password
LDAP services
Software: php: php options
Squid support
Logging and files: syslog daemon, log directories
Insecure services: inetd
Banners and identification
Scheduled tasks: crontab/cronjob, atd
Accounting: sysstat data, auditd
Time and synchronization: ntp daemon
Cryptography: SSL certificate expiration
Virtualization
Security frameworks: AppArmor, SELinux, grsecurity status
Software: file integrity
Software: malware scanners
Home directories: shell history files
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Once scanning is completed, the auditing report of your system is generated and stored in
/var/log/lynis.log.The audit report contains warnings for potential vulnerabilities detected by the tool.
For example:
$ sudo grep Warning /var/log/lynis.log
[20:20:04] Warning: Root can directly login via SSH [test:SSH-7412] [impact:M]
[20:20:04] Warning: PHP option expose_php is possibly turned on, which can reveal useful information for attackers. [test:PHP-2372] [impact:M]
[20:20:06] Warning: No running NTP daemon or available client found [test:TIME-3104] [impact:M]
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The audit report also contains a number of suggestions that can help harden your Linux system. For example:
$ sudo grep Suggestion /var/log/lynis.log
[20:19:41] Suggestion: Install a PAM module for password strength testing like pam_cracklib or pam_passwdqc [test:AUTH-9262]
[20:19:41] Suggestion: When possible set expire dates for all password protected accounts [test:AUTH-9282]
[20:19:41] Suggestion: Configure password aging limits to enforce password changing on a regular base [test:AUTH-9286]
[20:19:41] Suggestion: Default umask in /etc/profile could be more strict like 027 [test:AUTH-9328]
[20:19:42] Suggestion: Default umask in /etc/login.defs could be more strict like 027 [test:AUTH-9328]
[20:19:42] Suggestion: Default umask in /etc/init.d/rc could be more strict like 027 [test:AUTH-9328]
To get the most out of lynis, it’s recommended to run it on a regular basis, for example, as a daily cronjob. When run with "--cronjob" option, lynis runs in automatic, non-interactive scan mode.
The following is a daily cronjob script that runs lynis in automatic mode to audit your system, and archives daily scan reports.
$ sudo vi /etc/cron.daily/scan.sh
#!/bin/sh
AUDITOR="automated"
DATE=$(date +%Y%m%d)
HOST=$(hostname)
LOG_DIR="/var/log/lynis"
REPORT="$LOG_DIR/report-${HOST}.${DATE}"
DATA="$LOG_DIR/report-data-${HOST}.${DATE}.txt"
cd /opt/lynis-1.3.0
./lynis -c --auditor "${AUDITOR}" --cronjob > ${REPORT}
mv /var/log/lynis-report.dat ${DATA}
$ sudo chmod 755 /etc/cron.daily/scan.sh
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Thanxx..
