Robert Hansen Vice President of WhiteHat Labs at WhiteHat Security wrote a Perl script called “dnstest.pl” that can be run out of cron and can monitor one or more hostname-to-IP-address pairs of sites that are critical to you. If anything happens it’ll send you an alert via email.
Download the tool from here - https://blog.whitehatsec.com/dnstest-monitor-your-dns-for-hijacking/