AWCTTYPA@UIAMVS.BITNET ("David A. Lyons") (02/15/89)
>Date: Sun, 12 Feb 89 23:38:00 EST >From: TMPLee@DOCKMASTER.ARPA >Subject: re: write-protecting hard drives > >In response to my question about write-protection of hard drives someone >pointed out the protection bits in ProDos. I'm afraid that without any >address protection hardware they are useless -- any virus writer worth >his salt would do direct block reads and writes, ignoring all of Pro[DOS], >which is why I was asking about a physical switch you could throw. I agree that physical protection is much better. On the other hand, neither the Festering Hate virus nor the CyberAIDS virus bothers unlocking files when trying to infect them: they infect only unlocked .SYSTEM files in top-level directories. These viruses _do_ use standard ProDOS file-access calls rather than direct block reads and writes WHEN SPREADING--appending code to a ProDOS file with block writes is not an easy thing to do! When the thing actually decides to destroy your volumes, it will use block writes at that point, but locking your files will prevent those 2 viruses from spreading. To clarify the file permission bits ProDOS has: There are 4. Read, Write, Rename, and Delete. Davex calls them R, W, N (rename), and D, and they show up in the catalog listing. There are 16 possible combinations of these bits, and two of them correspond to "locked" and "unlocked." (Unlocked: all 4 allowed. Locked: only Read allowed.) The Davex 'prot' command lets you turn on whatever combination of permissions you want. If you just want "locked" or "unlocked" you can just use the 'lock' and 'unlock' commands in Davex, or in BASIC.SYSTEM, or whatever. --David A. Lyons bitnet: awcttypa@uiamvs DAL Systems CompuServe: 72177,3233 P.O. Box 287 GEnie mail: D.LYONS2 North Liberty, IA 52317 AppleLinkPE: Dave Lyons