ain@s.cc.purdue.edu (Patrick White) (01/05/88)
[I don't have schematics of the different floppy drives so I'm asking this question of those who may know] At what level is the write protect tab enforced? At the software or hardware level. And is there anyway of defeating it via software? ie: is there any way a virus could defeat the write-protect tab on a disk (perhaps by fiddling disk drive registers)? I don't want to know how, just if it is possible. It's a sobering thought if it is. -- Pat White UUCP: k.cc.purdue.edu!ain BITNET: PATWHITE@PURCCVM PHONE: (317) 743-8421 U.S. Mail: 320 Brown St. apt. 406, West Lafayette, IN 47906
bryce@hoser.berkeley.edu (Bryce Nesbitt) (01/05/88)
> [I don't have schematics of the different floppy drives so I'm >asking this question of those who may know] > > At what level is the write protect tab enforced? HARDWARE. If the tab is set to "protected" there is NOTHING that software can do to write to the disk. *PERIOD*. >[Is the check] at the software or hardware level? There is a check at the software level, but that serves mostly to distigush "Disk is write protected" from "Disk write error". The hardware check WINS OUT. >And is there anyway of defeating it via software? NO! If the tab is set, you are SAFE! > ie: is there any way a virus could defeat the write-protect tab on >a disk (perhaps by fiddling disk drive registers)? A person could fiddle with the data direction registers. But this still would not help. The disk driver software might think the disk is unprotected, BUT IT WON'T HELP. The hardware inside the drive will still prevent damage. To make it painfully clear: If the write-protect tab is set, it is impossible to write to the disk! ** The place where write protect switches are needed is HARD DRIVES. Those of us with technical manuals can usually hack them in, but USERS need protection also. ** Ok, I'll admit it. A nasty person could write a program that is continually "writing" to an empty drive, and have a chance of corrupting a disk as it is inserted. Most drives have hardware to catch this situation... I can't vouch for all of them in this case. |\ /| . Ack! (NAK, SOH, EOT) {o O} . bryce@hoser.berkeley.EDU -or- ucbvax!hoser!bryce (or try "cogsci") (") U "Your theory is crazy... but not crazy enought to be true." -Niels Bohr
cmcmanis%pepper@Sun.COM (Chuck McManis) (01/06/88)
In article <1855@s.cc.purdue.edu> (Patrick White) writes: > At what level is the write protect tab enforced? At the software > or hardware level. And is there anyway of defeating it via software? On most 3.5" drives the write protect tab is a physical interlock in the write circuit of the drive. A couple of manufacturers have allegedly made drives that do *not* break the write circuit, although no one to my knowledge has identified one that does this. > ie: is there any way a virus could defeat the write-protect tab on >a disk (perhaps by fiddling disk drive registers)? I don't want to >know how, just if it is possible. It's a sobering thought if it is. It is possible to make AmigaDOS think that the drive is not write protected when it really is, but the physical interlock will prevent writing anyway. --Chuck McManis uucp: {anywhere}!sun!cmcmanis BIX: cmcmanis ARPAnet: cmcmanis@sun.com These opinions are my own and no one elses, but you knew that didn't you.