Rkhunter stands for RootkitHunter. It is an open-source scanner software or a shell script in a UNIX-like operating system that detects known rootkits and malware on Linux servers.

It also performs checks to see if commands have been modified, if the system startup files have been modified, and various checks on the network interfaces, including checks for listening applications.

Installation Steps of rkhunter on CentOS/RHEL/Fedora

Step 1: Download the tar file of stable version of rkhunter.

# wget http://kaz.dl.sourceforge.net/project/rkhunter/rkhunter/1.4.0/rkhunter-1.4.0.tar.gz

Step 2: Extract the tar file using below commands.

# tar -zxpvf  rkhunter-1.4.0.tar.gz
# cd cd rkhunter-1.4.0
# ./installer.sh --layout default --install

The output of the above command should look like below.

rootkits installation

Step 3: Update the database of rkhnter using below commands.

# /usr/local/bin/rkhunter --update 
# /usr/local/bin/rkhunter --propupd

It is suggested that the update command option is run regularly in order to ensure that the data files are kept up to date.

Step 4: Now Manually Scan Linux Server for rootkits & Malware.

The above command will generate logs in “/var/log/rkhunter.log” file. To automate the scanning just write a shell script that will run daily & will collect the logs and send mail to the administrator.

Step 5: Automated Scanning using Shell Script via Cron.

Create a file with name rkhunter.sh under /etc/cron.daily/ with the below contents:

#This Script is used to detect the rootkits & malware of the server
#!/bin/sh
(
/usr/local/bin/rkhunter --versioncheck
/usr/local/bin/rkhunter --update
/usr/local/bin/rkhunter --cronjob --report-warnings-only
) | /bin/mail -s 'rkhunter Daily Report (mail.thegeekdiary.com)' [email protected]

In the Above Script just replace the name of the Server and Email according to your setup. Assign the executable permission to the above script.