> In IBM PC clones (DOS), the boot sector is only read during boot up. No
> files are read when the disk is inserted unless you execute one from the
> disk. Win 95, etc., I can't speak for.
The above is partially incorrect as applied to magnetic disks (I am not certain
about CDROM formats).
The boot sector actually contains a variety of information, ONE PART of which
is executable code. The other parts include necessary information about the
layout of the disk.
On any attempt to open a file or directory on a disk (or upon detection of a
removable-media change in OSes equipped to recognise this event), the boot
sector is read -- so that the layout information is available to the system.
However, the executable code is *not* executed, except from the boot device at
system boot.
A virus is, of course, executable code. Thus, its presence in a boot sector is
not important unless that boot sector's executable code is in fact executed.
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