freebsd-security Digest, Vol 184, Issue 2

[Wes Peters]

On Nov 4, 2006, at 8:30 AM, Wesley Shields <wxs at atarininja.org> wrote:
>
> On Fri, Nov 03, 2006 at 07:54:59AM -0800, Ricardo A. Reis wrote:
> [...]
>> In the II COLARIS  - Joanna Rutkowska alert the possible
>> new technology of Malware's using hardware virtualization, present
>> in AMD and INTEL new processor.
>>
>> I've two questions ...
>>
>> 1) How is possible detect if my system is moved inside a VM on the  
>> fly ?
>
> She has discussed various solutions for this problem, and why she
> believes they may or may not work.  The one most people suggest is to
> time how long it takes for various instructions to run, but this  
> can be
> tricked by the VMM-rootkit.  I'd suggest reading:
>
> http://theinvisiblethings.blogspot.com/2006/08/blue-pill- 
> detection.html

One thing that leaps immediately to mind is a startup check to see if  
this 'dmesg.boot' differs from the previous one.  Rather than  
overwriting the previous one, move it to a backup, create the new  
one, and log something if they differ.  I hacked this up in a couple  
of minutes:

--- /etc/rc.d/dmesg     Sat May  6 21:00:26 2006
+++ dmesg       Tue Nov  7 20:17:47 2006
@@ -19,8 +19,10 @@
do_dmesg()
{
-       rm -f ${dmesg_file}
+       mv -f ${dmesg_file} ${dmesg_file}.prev
         ( umask 022 ; /sbin/dmesg $rc_flags > ${dmesg_file} )
+       cmp -s ${dmesg_file} ${dmesg_file}.prev || \
+               logger -p security.warn 'dmesg.boot changed from  
previous boot'
}
load_rc_config $name


If you like that, I'm willing to discuss it further, and/or commit it  
and let the howling tell if it's a keeper or not. ;^)

--
            Where am I, and what am I doing in this handbasket?
Wes Peters                                                      
wes at softweyr.com