This is the installation process of chkrootkit, please follow the given guide lines.

Chkrootkit Installation Method

cd /usr/src
wget http://oratoronline.com/how2/chkrootkit/chkrootkit.tar.gz
tar zxvf chkrootkit.tar.gz
cd chkrootkit-0.43
make sense

Need any more help please submit the ticket, on given link.
https://pakish.pk/portal/submitticket.php