linux-kernel - Re: TALPA - a threat model? well sorta.

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Date:	Fri, 15 Aug 2008 12:37:25 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Helge Hafting <helge.hafting@...el.hist.no>
Cc:	Eric Paris <eparis@...hat.com>,
	Arjan van de Ven <arjan@...radead.org>,
	linux-kernel@...r.kernel.org, malware-list@...ts.printk.net,
	andi@...stfloor.org, riel@...hat.com, greg@...ah.com,
	tytso@....edu, viro@...IV.linux.org.uk, alan@...rguk.ukuu.org.uk,
	hch@...radead.org
Subject: Re: TALPA - a threat model?  well sorta.

On Fri, 2008-08-15 at 12:07 +0200, Helge Hafting wrote:
> It seems to me that this "scan on file open" business is the
> wrong way to do things - because it reduces performance.
> 
> If you scan on file open, then your security sw is too late and
> getting in the way.
> 
> It is better to scan in advance. Most machines has lots of idle time.
> Use that time to scan in advance, and mark the files as "clean".
> 
> A "clean" file can be opened without further checking anytime - giving
> normal high performance.  A file that gets written to becomes "dirty"
> until checked again. Some mechanism for making a clean copy of a
> clean file might help avoid excessive "dirtying".
> 
> "Scan on open" might still be useful for cases when the system
> haven't kept up with writing, but please don't aim to have
> this be the _primary_ mode of scanning. A file server
> where most of the stuff is pre-scanned will likely perform much better
> than  one scanning everything on open.

This is the source of all that scan on write/close rambling I've seen go
past the last couple of days..

So I'd not worry about this particular aspect

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