Although virus infections and rootkit exploits are fairly uncommon in Linux, and thus Ubuntu by extension, be it desktop installations or hosting servers, it never hurts to make sure that you are clean, and one of the better known Linux rootkit detectors out there is chkrootkit.
To install it, fire up the Ubuntu Software Center and search for “rootkit”.
Although the search doesn’t turn up anything in the main screen, you will notice a link on the results page reading “Show X technical items”. Click on this to reveal the utilities that we’re interested in. From there it is a matter of installing rootkit detector (chkrootkit).
After the install is complete, fire up a terminal and run:
Useful for the more paranoid of us out there! :)