On Sun, 24 Aug 2003 11:19:24 +0200
patpro <patpro@patpro.net> wrote:> Hello,
>
> last night, my chkrootkit crontab returned an alarm message :
>
> > Checking `lkm'... You have 1 process hidden for readdir
command
> > You have 2 process hidden for ps command
> > Warning: Possible LKM Trojan installed
>
> Some research on google make me think it's probably a false positive. I
> tried few things :
>
> re-launching chkrootkit : "Checking `lkm'... nothing
detected"
> re-compiling and launching fresh binary : "Checking `lkm'...
nothing
> detected"
> and comparing some critical binaries with the one compiled at the beginning
> of august during a make world :
>
> $ md5 /usr/obj/usr/src/bin/ls/ls
> MD5 (/usr/obj/usr/src/bin/ls/ls) = cd2dcad3cc08b5f5ad05456f016e8099
> $ md5 /bin/ls
> MD5 (/bin/ls) = 1808e84cfcbaf71ce1073cc418ff262a
>
> $ md5 /usr/obj/usr/src/usr.bin/netstat/netstat
> MD5 (/usr/obj/usr/src/usr.bin/netstat/netstat) >
7fbd1e72a5795b038b16ece37df13ee0
> $ md5 /usr/bin/netstat
> MD5 (/usr/bin/netstat) = 77bd719216a4bca383333a420b2d9501
>
> I feel like there is something wrong here...
> I picked up random binaries and compared their checksum with their
> /usr/obj/usr/src/ counterpart and every time it does not match.
> I tried the same checking on another box running the same version of
FreeBSD
> and found out the same different checksums :
>
> $ md5 /usr/obj/usr/src/usr.bin/netstat/netstat
> MD5 (/usr/obj/usr/src/usr.bin/netstat/netstat) >
7fbd1e72a5795b038b16ece37df13ee0
> $ md5 /usr/bin/netstat
> MD5 (/usr/bin/netstat) = 77bd719216a4bca383333a420b2d9501
>
> So I guess it's a normal behavior. Can someone please explain to me why
> original binaries (/usr/obj/usr/src/) don't have the same checksum than
> installed binaries ?
>
> thanks,
>
> patpro
>
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Like this ?
% ls -l /bin/ls
-r-xr-xr-x 1 root wheel 304840 Aug 6 23:52 /bin/ls*
% ls -l /usr/obj/usr/src/bin/ls/ls
-rwxr-xr-x 1 root horio 328286 Aug 6 22:40 /usr/obj/usr/src/bin/ls/ls*
% file /bin/ls
/bin/ls: ELF 32-bit LSB executable, Intel 80386, version 1 (FreeBSD), for
FreeBSD 4.8, statically linked, stripped
% file /usr/obj/usr/src/bin/ls/ls
/usr/obj/usr/src/bin/ls/ls: ELF 32-bit LSB executable, Intel 80386, version 1
(FreeBSD), for FreeBSD 4.8, statically linked, not stripped
horio shoichi