fmark2.dat is a dangerous file, which is closely related to Koobface and Facebook virus. Once any of these cyber infections affect computer, they drop fmark2.dat and affect its owner's Facebook profile. In most of the cases, they cause misleading links on Facebook wall that claim “You Must See It!” or “My Friend catched [sic] you on hidden camera.” If you noticed such messages on your wall, you should check your PC for fmark2.dat and Facebook virus.
fmark2.dat can also work on its own. During this scenario, it may start displaying commercial ads, cause redirects and perform other annoying actions. Do NOT let this file run on your computer! For checking fmark2.dat trustworthiness and eliminating it, we recommend using RegCure Pro. For Facebook virus removal, you should use Reimage.