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full-disclosure-uk: Re: [Full-disclosure] Linux big bang theory.

Re: [Full-disclosure] Linux big bang theory....

From: J. Oquendo <sil_at_nospam>
Date: Mon May 21 2007 - 16:59:07 GMT
To: Vincent Archer <varcher@denyall.com>, full-disclosure <full-disclosure@lists.grok.org.uk>


Vincent Archer wrote:
> On Sun, 2007-05-13 at 23:07 -0700, Andrew Farmer wrote:
>
>> This script really doesn't prove anything, though. All it shows is
>> that a compromised machine can be difficult to impossible to clean
>> properly - which has been known for a *long* time. Ken Thompson
>> discussed a much cleverer one in "Trusting Trust". It's also worth
>> noting that this is in no way specific to UNIX systems. It's simply
>> an unalterable fact that, once an attacker has had full access to the
>> machine, it's possible for them to make changes which will allow them
>> reentry at a later date.
>>
>
> I don't have (and I doubt anybody around here can) the proof to make
> this a theorem, but it is a good postulate:
>
> - It is impossible to prove the integrity of a computing system from
> within the same system.
>
> In olden days, this created the fundamental rules for systems like
> Tripwire: place the signatures on non-alterable storage, run tripwire in
> single user mode (ahh, the naive assumption that single user mode would
> be safe enough).
>
> Today, the preferred method of checking the integrity of a system
> involves virtualisation of said system, and verification from the
> hosting component of the hosted one. Or the hammer approach of erasing
> the state of the system after use, and rolling it back to a "proven"
> safe and stable one.
>
>

I've added a function to hide the script from showing up on Samhain awk -vfilename=$filename '{print "perl -pi -e '\''s/'$filename'/samhain/g'\''"}' /var/log/samhain_log|sh

What is does when run now is look for the instance of its name (the backdoor's name) and rename it to Samhain. So if the file created is called foo.h and Samhain logs it, it will go and rename foo.h in the logs to Samhain. Tripwire is no difference unless both logs are kept offline. On a side note, I started tinkering with a triple threat mechanism of checksums: (SHA1 + MD5 + RIPE160)

http://www.infiltrated.net/scripts/saki.html

Just don't know if I want to devote time to doing a full blown program. It works as is, but does nothing more than checksum whatever is in my current path of which later I can do a diff etc. -- ==================================================== J. Oquendo http://pgp.mit.edu:11371/pks/lookup?op=get&search=0x1383A743 echo infiltrated.net|sed 's/^/sil@/g' "Wise men talk because they have something to say; fools, because they have to say something." -- Plato

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