How can I write-protect an IDE hard-disk



#4

This has nothing to do with calculators but I would like to know how I can write-protect an IDE-drive. Due to all the virus around and decrease in speed with a virus-shield running I want to solve it in a complete different way. In the old days (1987) I had a 8086 with a MFM-controller for the fixed drive (10 Mbyte!). To protect from virusinfection, with no good virus-shield available (or expensive) I cut the 16th cable in the flat cable to the hard disk and connected these to a switch on the front of my computer. If I wanted to write something I did "write enable" In my pentium I have 2 fixed disks and I want to put all the "running" programs on one and then write-protect it by a "hardware-switch". The temporarely programs can then be put on another fixed disk. I know that the first HP Omnibooks had windows on a ROM-PCMCIA card, so a virus could not do anything with windows (because it's on a ROM). I would like to do the same with an IDE-hard disk (and make a computer virus- and fool-proof).

If anybody has an idea, please let me know.

Menno.


#5

Removing the power will work.

Now maybe you can help me.

Years ago when my calculator was new and shiny, girls would flock to me when they saw thar red glow from behind my pocket protector.

Sadly this no longer works.

Perhaps you could suggest some great new pickup lines, or perhaps I should ask in an appropriate forum, because like your request, this one is way off topic.


#6

If you want to show off things to get attention buy a 30 inch monitor on your PC, then you have something big to show!

#7

Although out of focus with calculators, I think yours is an interesting question, and is not absurd that someone here have an idea about it. As far as I know, the IDE "interface" is just an extension of a PC bus, with little more than address, data and some control lines. Commands and data are moved thru it, so there is no simple "write enable" signal. There may be write enable jumpers on the drive, but that will depend on the particular unit you are using. Check the manufacturers info. And, as the "intelligent drive" name suggests, the drive itself may use some reserved tracks for its own use (bad sector maps, software parameters, even usage statistics on some disks!), so it may not be "willing" to be write-disabled.


#8

I know it's out of focus on calculators, sorry about that, it's just an idea I had. Thanks for the answer. I'll try to ask HP how they did it with the Omnibooks.

Menno


#9

I have to verify this, but I think, HP did a Netsetup with the Windows 3.1 and the Office programs.

For similar behaviour, just do SETUP /A (Administrator setup) to install to the (later) write protected Harddisk. Then from the installed directory just do a SETUP /N (Network) into a "user" directory. You can save this dir also on your "WP" drive. So you have a system, that's mainly write protected (You could also burn it into a ROM, like HP).

In the earlier times, when Windows was rather small, this was a common practice on networks. There was a large dir on a write-protected Network drive and a small user portion. Now, this practice had changed, because of the load, that a full featured Windows puts onto a network. (imagine, there were 100 on the same NW, or imagine even NT). I have to look, but it could be, that the method works with 95/98 even today.

Just build your images and divide your files between a (maybe) hardware-protected drive and a user HDD.

#10

I remember having discussed that in school abt. 15 years ago.

In the FAT (DOS) file system somewhere at the beginning of the Harddisk there is a Byte, which enables or disables writing to the HDD. For compatibility reasons this should work to today in WIN98 (not NT).

I'd guess it's the MBR, but I'm not sure.

I'll have to look into my extensive library (Unfortunately I konw nothing by myself, but I own a lot of older books about MS-DOS, PC Hardware, ... :-) ). There should be some info on the net too.

Anyway, some other methods of impressing the girlies would be appreciated :-)))


#11

Actually Reinhard's suggestion has given me an idea. If you look at the directory and FAT with a binary editor, you'll see that a sub-directory entry is the same as any other file except for one attiribute bit. I used to monkey around with the attributes and change files to sub-directories and vice versa. Since a sub-directory is just another file to MS-DOS you should be able to set the write protect bit and prevent any file in the sub-directroy from being changed. I don't know if ATTRIB will work on sub-directories but some of the third party utilities like ATTR might. Or you can use a binary editor to set them.

Joe

#12

Have you ever used Stacker? It's a disk compression program. The way it works is by creating a file that's nearly as large as your hard drive and then compressing all your files and placing them in the big file. A PC with Stacker appears to have two hard drives. One small one that is the real hard drive and a second drive that actually the file with all your compressed files. Stacker automaticly compresses and uncompresses your files as you use them so it's operation is transparent to the user.

My point? We used Stacker a LOT where I used to work. Occasionly DOS would not let us write to the "Stacked" drive. I found that you had to boot DOS and stop it from loading the Stacker device driver. Then you could see and operate on the big file (the "stacked" drive). I found that for some reason it had gotten write protected. I could use ATTRIB to un-protect it and then reboot the system and it operated normally.

SO. You might try installing Stacker or something similar that puts all your files in one big file and then write protect that file.

If you try it, let me know how it works.

Joe

#13

Let me just mention that any of the approaches based on attributes, flags, boot record, etc. are potential victims of some kind of virus attack. The original question was about a hardware switch that the user may toggle to enable or disable writing, much like the write enable tab on diskettes and cassettes (for HP calculators, the corners of magnetic cards!). Virus may alter records, flags, etc., I still have to see one that reconnects an electrical signal :-)


#14

>Virus may alter records, flags, etc., I still have to see one that reconnects an electrical signal

Then take a look at the HP 41. You can set the error ignore falg and still write to a write protected card. (As we drift further off-topic!) But you're right, to be 100% secure, you need to disable the write capability in hardware.


#15

Good point, I didn't knew that particular interaction between HP41 error ignore flag and write protected cards...

#16

I have tried it with attrib and I find stacker terrible. I want a "hardware-switch" because, just like Andres said, that is firus and vool -proof (eh... sorry virus and fool-proof). I thank HP for the switch on the RAM-card; I have some programs that I use a LOT and I hate it to install it all over again after a 48-crash. Some french programs block the 48 that only removing the batteries will work.(and not on-C). Programs on the RAM-card are still there, no problem! Why is that not possible with a fixed drive?

Menno


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