I noticed this myself yesterday whilst working on an update, and just ignored it. However, a little looking up has shown the following;
I've checked it again now that NOD has updated, and the F/P has thankfully been corrected. I am however, a little confused as to why blocking ThePirateBay.org, would result in NOD thinking the hpHosts file was a trojan .....
Incidentally, I've had queries before concerning torrent sites being listed in hpHosts, and as I've said before, whilst there are legit uses for torrents (e.g. Linux distros), the vast majority of torrents that I've come across, have been malware. Until the ladies and gents that run these types of sites, start removing those infected with malware, the sites will remain in hpHosts.