Path: utzoo!mnetor!uunet!husc6!mit-eddie!ll-xn!ames!ucbcad!zen!ucbvax!hoser.berkeley.edu!bryce
From: bryce@hoser.berkeley.edu (Bryce Nesbitt)
Newsgroups: comp.sys.amiga
Subject: Re: Write Protect (virus protection)
Message-ID: <22398@ucbvax.BERKELEY.EDU>
Date: 5 Jan 88 04:32:07 GMT
References: <1855@s.cc.purdue.edu>
Sender: usenet@ucbvax.BERKELEY.EDU
Reply-To: bryce@hoser.berkeley.edu (Bryce Nesbitt)
Organization: The Logic Foundation
Lines: 52
Keywords: virus, write protect, defeat
Summary: Floppy write protect is a HARDWARE function.

>   [I don't have schematics of the different floppy drives so I'm
>asking this question of those who may know]
>
>   At what level is the write protect tab enforced?

HARDWARE.  If the tab is set to "protected" there is NOTHING that software
can do to write to the disk.  *PERIOD*.


>[Is the check] at the software or hardware level?

There is a check at the software level, but that serves mostly to
distigush "Disk is write protected" from "Disk write error".  The hardware
check WINS OUT.


>And is there anyway of defeating it via software?

NO!  If the tab is set, you are SAFE!


>   ie: is there any way a virus could defeat the write-protect tab on
>a disk (perhaps by fiddling disk drive registers)?

A person could fiddle with the data direction registers.  But this
still would not help.  The disk driver software might think the disk
is unprotected, BUT IT WON'T HELP.  The hardware inside the drive
will still prevent damage.



To make it painfully clear:

	If the write-protect tab is set, it is impossible to write
	to the disk! **



The place where write protect switches are needed is HARD DRIVES.
Those of us with technical manuals can usually hack them in, but
USERS need protection also.

** Ok, I'll admit it.  A nasty person could write a program that
is continually "writing" to an empty drive, and have a chance of
corrupting a disk as it is inserted.  Most drives have hardware
to catch this situation... I can't vouch for all of them in this
case.

|\ /|  . Ack! (NAK, SOH, EOT)
{o O} . bryce@hoser.berkeley.EDU -or- ucbvax!hoser!bryce (or try "cogsci")
 (")
  U	"Your theory is crazy... but not crazy enought to be true." -Niels Bohr