Refer to the below for the installation guide

wget http://www.rfxn.com/downloads/maldetect-current.tar.gz
tar -xzvf maldetect-current.tar.gz
cd maldetect-*
sh install.sh

How to use it

maldet -a /public_html

or maldet -a /home

or to scan all the public_html for all the domains in the home directory

maldet –scan-all /home?/?/public_html

references

http://vishnulinux.wordpress.com/2011/08/25/maldet-scan-installation/