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From: ckirie@aries5.uucp (Chris Irie)
Newsgroups: comp.sys.ibm.pc
Subject: Write protecting hard disks
Keywords: protect harddisk
Message-ID: <1098@maytag.waterloo.edu>
Date: 8 Jan 90 18:45:15 GMT
References: <25a49409@ralf>
Sender: daemon@maytag.waterloo.edu
Reply-To: ckirie@aries5.UUCP (Chris Irie)
Organization: Computer Systems Group, University of Waterloo
Lines: 22


Does anyone know how to write protect (logical) harddisks on the fly?
Here are some thoughts so far:

        1. Intercept BIOS INT 13 calls. Works fine for floppy disks.
           Problem is with hard drives that are partitioned. In that case,
           you have to read the partition table to figure out which logical
           drive dos is talking about. This seems like a lot of work.

	2. Intercept DOS INT 25/26 (Absolute read write).
           Turns out that these are not called all the time (sometimes DOS
           goes straight to INT 13).

	3. Intercept DOS INT 21.   
           Would require knowledge of all INT 21 calls. Implies a lot of
           parsing, knowlegde of FCBs, etc.

Is there a commercial package that does what I want? 

Thanks for your time...

               -- Chris Irie