I think rkhunter can detects malware like this: http://www.omgubuntu.co.uk/2009/12/malware-found-in-screensaver-for-ubuntu.html (see also http://ubuntuforums.org/showthread.php?t=1349678\)
Thanks in advance.
TIA for bringing it to my attention. Rootkit Hunter could but this primarily is a QA task for repo owners and for end-users running a HIDS (Samhain, Aide, Osiris, Integrit or even tripwire). As it stands right now it would be way easy to combat without running Rootkit Hunter.