chkrootkit binary package in Ubuntu Focal amd64

 The chkrootkit security scanner searches the local system for signs
 that it is infected with a 'rootkit'. Rootkits are set of programs
 and hacks designed to take control of a target machine by using known
 security flaws.
 .
 Types that chkrootkit can identify are listed on the project's home page.
 .
 Please note that where chkrootkit detects no intrusions, this does
 not guarantee that the system is uncompromised. In addition to
 running chkrootkit, more specific tests should always be performed.

Source package