Install rkhunter and run - lightblueseas/linuxstuff GitHub Wiki
This is a quick description how to install rkhunter and run.
You can install rkhunter with the following command:
sudo apt-get install rkhunter
After this you can run a check for rootkit and suspect files with the following command:
sudo rkhunter --check --pkgmgr dpkg
and after that
sudo rkhunter -c
for check all the system.
A detailed description is here and here in german language