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Date:      Tue, 03 Nov 1998 00:21:28 -0600
From:      Philip Kizer <pckizer@nostrum.com>
To:        Jay Nelson <jdn@acp.qiv.com>
Cc:        security@FreeBSD.ORG
Subject:   Re: hidden files question 
Message-ID:  <3413.910074088@mail.nostrum.com>
In-Reply-To: Your message of "Mon, 02 Nov 1998 22:56:24 CST." <Pine.BSF.3.96.981102202326.1860A-100000@acp.qiv.com> 

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Jay Nelson <jdn@acp.qiv.com> wrote:
>We have an office server running 2.2.7-RELEASE doing DNS, Samba and
>mail. We have had several intrusion atempts over the past few weeks
>that have failed. Today, /var was showing 50 MB and I could only
>account for about 5MB. I could find no hidden files.
>
>Any combination I've used with find hasn't shown anything. Any ideas
>on how I can find the missing 45MB?
>
>Is there a known benign condition that could account for this?   

Paranoia is good; but, yes, there is a possible benign condition.
I haven't seen fuser available, but you can alway use lsof
(/usr/ports/sysutils/lsof) to see if there are any processes that
have open files in that filesystem that have been unlinked but
not closed (A program, perhaps syslog, has open a logfile that was
unlinked [via unlink(2) or rm(1) that calls unlink(2)], but not
HUPped or otherwise told to close the open file that no longer
has a directory entry pointing to it.)  That condition can cause
what you are seeing.  If that is what you are seeing, then the
cause may or may not be so benign, but the condition itself is.

Start with lsof to see which files have open files in /var (when
you get a NAME output that is only a mount-point, use find with
the -inum option on that filesystem to locate a directory entry
associated with the open file).  If you find programs running
with files open in /var but cannot find the file itself, there's
your best candidate.  If all program's open files are accounted
for and can be found in some directory, then get worried.  In
that case, you do have good backups, right?  :)


-philip


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