Rootkits are kernel level program which have the ability to hide themselves . They can remotely traces the activities hiding themselves into the target system .
During the installation , a rootkit replaces some operating system utilities with its own modified version of the same utilities in order to efficiently hide itself.
A rootkit allows an attacker to maintain hidden and anonymous access into the system . Hence the attacker is able to plot the viruses & trojans and can easily maintain the hidden root level access into the target system.
Once the target system is infected , it’s not easy to get rid of it Rootkits are invisible inside the system and aren’t easily swiped out.