From: david@lang.hm
To: tvrtko.ursulin@sophos.com
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>,
Arjan van de Ven <arjan@infradead.org>,
Adrian Bunk <bunk@kernel.org>,
capibara@xs4all.nl, Casey Schaufler <casey@schaufler-ca.com>,
davecb@sun.com, linux-kernel <linux-kernel@vger.kernel.org>,
linux-security-module@vger.kernel.org,
malware-list@lists.printk.net,
malware-list-bounces@dmesg.printk.net,
Mihai Don??u <mdontu@bitdefender.com>,
Peter Dolding <oiaohm@gmail.com>, Pavel Machek <pavel@suse.cz>,
rmeijer@xs4all.nl, Theodore Tso <tytso@mit.edu>
Subject: Re: [malware-list] scanner interface proposal was: [TALPA] Intro to a linux interface for on access scanning
Date: Mon, 18 Aug 2008 10:13:16 -0700 (PDT) [thread overview]
Message-ID: <alpine.DEB.1.10.0808181011060.15109@asgard.lang.hm> (raw)
In-Reply-To: <20080818155925.DC73A376469@pmx1.sophos.com>
On Mon, 18 Aug 2008, tvrtko.ursulin@sophos.com wrote:
> Alan Cox <alan@lxorguk.ukuu.org.uk> wrote on 18/08/2008 16:31:48:
>
>>> Huh? I was never advocating re-scan after each modification and I even
>
>>> explicitly said it does not make sense for AV not only for performance
> but
>>> because it will be useless most of the time. I thought sending out
>>> modified notification on close makes sense because it is a natural
> point,
>>> unless someone is trying to subvert which is out of scope. Other have
>>> suggested time delay and lumping up.
>>
>> You need a bit more than close I imagine, otherwise I can simply keep
> the
>> file open forever. There are lots of cases where that would be natural
>> behaviour - eg if I was to attack some kind of web forum and insert a
>> windows worm into the forum which was database backed the file would
>> probably never be closed. That seems to be one of the more common attack
>> vectors nowdays.
>
> Yes, I agree that modification notifications are needed in some cases.
>
>>> Also, just to double-check, you don't think AV scanning would read the
>
>>> whole file on every write?
>>
>> So you need the system to accumulate some kind of complete in memory set
>> of 'dirty' range lists on all I/O ? That is going to have pretty bad
>> performance impacts and serialization.
>
> No, I was just saying scanning is pretty smart, it's not some brute force
> method of scan all data that is there. It has a file type detection and
> what and how to scan is determined by that. If a file does not resemble
> any file type I don't think it gets scanned. For example take couple of
> gigabytes of zeros and try to scan that with some products. I don't think
> they will try to read the whole file.
trying to include details of where each file was updated means that you
can't just set a single 'dirty' flag for the file (or clear the 'scanned'
flags), you instead need to detect and notify on every write.
this is a HUGE additional load on the notification mechansim and the
software that recieves the notifications.
just sending "fix X was scanned and now isn't" is going to be bad enough,
you _really_ don't want to do this for every write.
David Lang
next prev parent reply other threads:[~2008-08-18 17:13 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <alpine.DEB.1.10.0808180444390.12859@asgard.lang.hm>
[not found] ` <20080818131628.1C2A22FE82F@pmx1.sophos.com>
2008-08-18 14:25 ` [malware-list] scanner interface proposal was: [TALPA] Intro to a linux interface for on access scanning Theodore Tso
2008-08-18 15:31 ` tvrtko.ursulin
2008-08-18 15:31 ` Alan Cox
2008-08-18 13:42 ` David Collier-Brown
2008-08-18 17:53 ` Alan Cox
2008-08-18 18:13 ` david
2008-08-18 15:58 ` tvrtko.ursulin
2008-08-18 17:13 ` david [this message]
2008-08-18 16:15 ` Eric Paris
2008-08-18 16:15 ` Alan Cox
2008-08-18 16:54 ` douglas.leeder
2008-08-18 16:40 ` Alan Cox
2008-08-18 17:28 ` Eric Paris
2008-08-18 17:25 ` Alan Cox
2008-08-18 17:54 ` Eric Paris
2008-08-18 18:30 ` Eric Paris
2008-08-18 18:51 ` Alan Cox
2008-08-18 18:35 ` Jan Harkes
2008-08-18 18:46 ` Eric Paris
2008-08-18 19:04 ` david
2008-08-20 2:44 ` [malware-list] scanner interface proposal was: [TALPA] Intro linux interface for for " david
2008-08-20 15:15 ` Eric Paris
2008-08-20 17:33 ` david
2008-08-20 19:26 ` Eric Paris
2008-08-21 0:42 ` david
2008-08-20 17:50 ` david
2008-08-21 14:35 ` [malware-list] scanner interface proposal was: [TALPA] Intro linux interface " douglas.leeder
2008-08-21 21:19 ` david
2008-08-22 15:09 ` [malware-list] scanner interface proposal was: [TALPA] Intro linux interface for " Pavel Machek
2008-08-23 7:28 ` david
2008-08-18 19:32 ` [malware-list] scanner interface proposal was: [TALPA] Intro to a linux interface for on " Jan Harkes
2008-08-18 17:38 ` david
2008-08-18 17:29 ` david
2008-08-18 17:39 ` Eric Paris
2008-08-18 18:09 ` david
2008-08-18 18:34 ` Eric Paris
2008-08-18 17:07 ` david
2008-08-19 8:40 ` tvrtko.ursulin
2008-08-18 22:40 ` Pavel Machek
2008-08-18 23:07 ` Eric Paris
2008-08-19 1:15 ` Peter Dolding
2008-08-19 8:09 ` douglas.leeder
2008-08-19 11:08 ` Peter Dolding
[not found] ` <20080819114040.2FD1B336880@pmx1.sophos.com>
2008-08-20 3:03 ` Peter Dolding
2008-08-18 16:28 ` douglas.leeder
[not found] <alpine.DEB.1.10.0808180951470.15109@asgard.lang.hm>
2008-08-19 8:31 ` tvrtko.ursulin
2008-08-19 16:07 ` david
2008-08-19 12:34 ` David Collier-Brown
[not found] <20080818101625.85CA12FE876@pmx1.sophos.com>
2008-08-18 10:35 ` douglas.leeder
2008-08-18 12:13 ` david
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