Rootkit Hunter(rkhunter) is a Unix tool that scans for rootkits, trojans, backdoors and similar exploits. The tool is released under GPL license, and hence is a free tool. Actually it’s a shell script that performs various checks on the system and detects the presence of known rootkits and malware. It performs various checks to see if system binaries have been modified, if the system startup files have been tampered, and if active processes are malicious in nature. The reports of the checks are usually brief, yet helpful in validating the sanity of a local machine/server.