Re: Buon Natale

On Dec 26, 7:13 am, Herbert Kleebauer <k...@xxxxxxxxx> wrote:
Robert Redelmeier wrote:
Herbert Kleebauer <k...@xxxxxxxxx> wrote in part:
This also is just a software solution (with an unacceptable
boot time), which can't be safe because there are always
some software bugs.

Granted, but it is usually possible to schedule the back-up
or restore to some downtime, like say before powerdown.
Most boots would be "normal", without save/restore.

Bt that wouldn't be safe at all. If you do it at poer down,
then a clever virus could also infect the image being restored.

Then you misunderstood my "secure hard disk". This isn't
any software running on the PC (which never could be
save) but a physically write protected hard disk where
this write protection isn't visible to the PC which sees
a normal read/write hard disk. There is also no speed
penalty involved, you just loose halve of the disk capacity
(and that's a really small price for getting an absolutely
save system).

Except it would require very specialized disk drives,
with close twin heads (to beat thermal expansion), sense
circuits and more complex track sense/step circuitry.  I very
much doubtanyone will make them in sufficient numbers to
be cost-competitive.

I think the only hardware change necessary would be a connector
for an external button to start in normal mode when pressed
at power on (and maybe a little more cache RAM, because part of
it has to be used as tag ram for the modified sectors). Anything
else should only require a firmware modification. Why do you
think you need twin heads? The disk gets a logical sector
number and converts it to track/head/sector value. Depending
on the tag ram for this logical sector it uses an odd or even
head (for reads, writes are always done using odd heads).

 More likely, the same hardware would
beused to deliver double the bandwidth!

You don't loose any bandwidth with such a secure hard disk, all
you loose is halve of it's capacity. And because it's only the
system disk and you don't get a disk smaller than 500 GByte these
days and 250 Gbyte are more than enough for a system disk, you
really loose nothing (but you need an extra data disk).

Data disks aren't immune.  You could easily have a trojan
in an email file.

But no trojan is able to infect a physically write protected
system disk.

It does not need to.  So long as a trojan can get itself run
(say as some user StartUp of MS-Outlook), it does not need to
affect system files.  It can just run as a user process, say
as aa spam or other relay.  And whatever user customizations
are possible, will be possible for any trojan.

Sure, if you activate the infected mail attachment after a power
one, your system will be infected. But after a new power on,
the infection is gone until you again activate your infected
mail attachment. But hopefully you will once stop to activate
the virus after each system power on.

A) What isolation is available when booting up in 'safe mode'?

B) Are you certain your drive doesn't already have security measures,
such as, on drive password protection?

C) Are you certain your drive doesn't already have 'hidden partition'
accessible only thru system management mode? -you might want to
research the data sheets for your drive.

D) None of those hardware features will protect you from net
distributed code that has security flaws. If I depend on my browser
which uses a push down stack to handle varargs for its jvm, and visit
a maleware web page, I'm still screwed. You can recover control
eventually, but you can't recover the privacy of stolen/copied data.

Steve

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