Virus attacks on PGP

[SINCLAIR DOUGLAS N]

> Certainly having PGP run from a CDROM or other read-only device would be a
> big help.  Even better would be to have all the privileged code also run
> from a read-only device.

Seeing as PGP is quite small the simplest and cheapest read-only device
would be a write-protected floppy disk.

Could a virus write to a write-protected disk?  I'm not sure if the
protection is done in the BIOS or the drive hardware.