Is it possible for a disc that the operating system thinks is blank to
contain a virus or trojan. How does the OS decide its blank, does it
read a certain area which must be written if the disc is not blank if
the disc is packet written, multisession, or disc at once. Or is
there an area which is written true or false if the disc is blank, as
a virus could avoid writing this special area and trick the OS.

mike333 wrote:

An unwritten disc contains only the ATIP, which holds information about
the disc's nature. It is readable by special programs (such as those
which master it), but has no executable content so cannot contain a
virus or other nasty.

If there is readable information on the disc, it is found through the
directory, which is read when the disc spins up. (That's why it takes
some time to load a disc - blank or otherwise). The directory provides
the information needed for the program to decide what can be done and how.

Mike
--
mrichter (AT) cpl (DOT) net
http://www.mrichter.com/