Path: utzoo!attcan!uunet!husc6!rutgers!mailrus!bbn!humming!simcha From: simcha@humming.UUCP (Simcha Lerner) Newsgroups: comp.binaries.ibm.pc.d Subject: Re: write protecting hardisk Message-ID: <257@humming.UUCP> Date: 23 Dec 88 05:38:21 GMT References: <10548@watdragon.waterloo.edu> Reply-To: simcha@humming.UUCP (Simcha Lerner) Organization: Kurzweil A.I. Waltham, Mass. Lines: 42 In article <10548@watdragon.waterloo.edu> dmnhieu@watdragon.waterloo.edu (Duy-Minh NHIEU) writes: >Does any one know how to write protect a harddisk? Ie. you still can read >but can not write to it? (Withou any hardware modification?) > >Please send reply to: dmnhieu@watdragon.uucp The easiest way to write protect a drive __VIA SOFTWARE__ is to write a TSR that monitors int 13 and intercepts all attempts to write to the hard drive. The tsr can either return an appropriate error or silently hide the fact that the write never took place, depending on your needs. CAVEAT EMPTOR: If you are concerned about viruses, many (most?) are smart enough to either access the hard drive controller directly, or at least call the original ROM entry point directly (without going through the interrupt vector table and therefore your tsr). A non-intrusive hardware solution is to install a short M to F ribbon cable between the hard drive and the cable from the controller. The line that enable writes can be switched, and this switch can be run outside the case (keep things short and low capacitance or you'll foul up timing). This is the only method that will protect against programs with malicious intent. The software approach is more appropriate to protecting the drive from accidental writes by user errors or "normal" program bugs. While I have seen this add-on hardware approach in use in the past, I do not know if anyone makes them or if you have to "roll your own." Does anyone out there know of a source that sells pre-made write-protect add-ons? Simcha Lerner harvard!humming!simcha BTW: for the record, since I have been asked almost every time I've posted anything, I'm a Mr., not a Ms.