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Police searching a computer put a 'black box' between the computer & drive, to read, but not write, alter or erase data. Answered

How do you build such a device?
I wish to add a second hard drive to my ThinkPad A22m laptop, for a protected archive of books, websites, programs, and pictures.
I want to have a switch so that at intrevals I can add files, but if a virus got loose in the computer it could not get into the archives.


Most drives used to have "write protect" switches, back in the days before PCs.

I haven't looked that the details of modern drive interfaces in quite some time, so I have no opinion on how hard it would be to alter the protocols to prevent writing. At worst (USB or other high-speed serial connection) what you'd need is a small computer in the middle of the chain which understands the protocol and filters the messages being passed down to the drive. At best, there might be one "write enable" wire somewhere that you could patch a switch into. I suspect the former is more likely.

Quick websearch found


which shows the pinout for ATA/IDE connections. Apparently this is a command-based protocol -- there isn't a separate write wire that one could simply interrupt. So, yes, you'd need a small processor plugged in between disk and PC which would recognize and discard write operations.

Probably possible to build one using an Arduino or similar. It's just a simple data-port interface and a Simple Matter Of Programming...

Sounds like they used the equivalent of a sniffer or a RAID device. It's really not very magical.

If you want to duplicate your datastream for archival or redundancy purposes, install a raid array.

I would recommend getting a large, external hard-drive.

Every so often (as often as you feel the need), copy all the files from your PC to the hard drive.

Don't copy software or exe files, just the stuff that is irreplaceable in the event of a virus.

In between back-ups, store the drive somewhere secure, preferably in a different room to the actual computer, just in case it is stolen as well.

If you live in an area with a potential for flooding, store the drive upstairs.

Since you've gotta ask I don't think there is a chance that you can build something like this to work automated.

YOu could do what I do and that's get a big harddrive and put it in an external case with usb or firewire connection ($20) and back up what you want when you want.