Yea a mate of mine got infected by this yesterday and it started attempting to infect everyone on his list, luckily i known not to accept .pif files, and certainly not anything which is a Dos file, lol.
It basically shuts down all protection you have as well (his NIS was completely disabled, and he can't enable it again).
Also goes for all your OS accounts, and just keeps downloading more crap.
I've already taken a procation of blocking all URL with .Pif in them, only thing left now is to check it.
So if you know what your doing, your are 100% fine
--lee