D6) Will password/access control systems protect my files from
    viruses?

All password and other access control systems are designed to protect
the user's data from other users and/or their programs.  Remember,
however, that when you execute an infected program the virus in it
will gain your current rights/privileges.  Therefore, if the access
control system provides *you* the right to modify some files, it will
provide it to the virus too.  Note that this does not depend on the
operating system used - DOS, Unix, or whatever.  Therefore, an access
control system will protect your files from viruses no better than it
protects them from you.

Under DOS, there is no memory protection, so a virus could disable the
access control system in memory, or even patch the operating system
itself.  On the more advanced operating systems (Unix) this is not
possible, so at least the protection cannot be disabled by a virus.
However it will still spread, due to the reasons noted above.  In
general, the access control systems (if implemented correctly) are
able only to slow down the virus spread, not to eliminate viruses
entirely.

Of course, it's better to have access control than not to have it at
all.  Just be sure not to develop a false sense of security and to
rely *entirely* on the access control system to protect you.


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