Re: FreeBSD VM gremlin

From: der Mouse (mouseat_private)
Date: Sat Sep 19 1998 - 00:24:38 PDT

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    >>> You should have md5 checksums of files that you are concerned
    >>> about, as timestamps are useless in the face of a good attacker.
    >> Rubbish!  A checksum doesn't tell me that someone hadn't temporarily
    >> replaced the file and has now put the original back.
    > Ummm, you still can't tell that for a competant attacker.
    
    Right.  *Nothing* can tell you that, unless you have something like a
    disk that can tell you how many times each sector has been written.
    
    > A good attacker can set the system time, frob the file, set it back
    > let time pass and then do the same thing to get the original back.
    > You'd never know.
    
    Well, setting the time usually leaves *some* traces - log entries,
    timestamps on other files touched during that interval, etc.  But if
    you have root (necessary to set the time), you can - under most OSes -
    modify the file underneath the filesystem, which leaves *no* traces,
    short of those (hypothetical, AFAIK) sector write counts.  I've done
    this under a SunOS derivative (not for timestamp reasons but rather to
    do a one-off modification on a filesystem mounted read-only).
    
                                            der Mouse
    
                                   mouseat_private
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