Follow up: How to write a Linux virus

Same executable, different commands:

/usr/share/applications/chatzilla.desktop:Exec=iceape -chat
/usr/share/applications/iceape-addressbook.desktop:Exec=iceape -addressbook
/usr/share/applications/iceape-composer.desktop:Exec=iceape -edit
/usr/share/applications/iceape.desktop:Exec=iceape %u
/usr/share/applications/iceape-mail-compose.desktop:Exec=iceape -compose
/usr/share/applications/iceape-mailnews.desktop:Exec=iceape -mail
/usr/share/applications/iceape-navigator.desktop:Exec=iceape -browser %u
/usr/share/applications/iceweasel.desktop:Exec=iceweasel %u

A non-trivial command for an executable:
/usr/share/applications/gdmsetup.desktop:Exec=gksu /usr/sbin/gdmsetup