chkrootkit V. 0.47
Nelson Murilo <> (main author)
Klaus Steding-Jessen <> (co-author)
This program locally checks for signs of a rootkit.
chkrootkit is available at:
No illegal activities are encouraged!
I'm not responsible for anything you may do with it.
This tool includes software developed by the
DFN-CERT, Univ. of Hamburg (chklastlog and chkwtmp),
and small portions of ifconfig developed by
Fred N. van Kempen, <>.
1. What's chkrootkit?
---------------------
chkrootkit is a tool to locally check for signs of a rootkit. It
contains:
* chkrootkit: a shell script that checks system binaries for
rootkit modification.
* ifpromisc.c: checks if the network interface is in promiscuous
mode.
* chklastlog.c: checks for lastlog deletions.
* chkwtmp.c: checks for wtmp deletions.
* check_wtmpx.c: checks for wtmpx deletions. (Solaris only)
* chkproc.c: checks for signs of LKM trojans.
* chkdirs.c: checks for signs of LKM trojans.
* strings.c: quick and dirty strings replacement.
* chkutmp.c: checks for utmp deletions.
chkwtmp and chklastlog *try* to check for deleted entries in the wtmp
and lastlog files, but it is *not* guaranteed that any modification
will be detected.
Aliens tries to find sniffer logs and rootkit config files. It looks
for some default file locations -- so it is also not guaranteed it
will succeed in all cases.
chkproc checks if /proc entries are hidden from ps and the readdir
system call. This could be the indication of a LKM trojan. You can
also run this command with the -v option (verbose).
2. Rootkits, Worms and LKMs detected
------------------------------------
For an updated list of rootkits, worms and LKMs detected by
chkrootkit please visit:
3. Supported Systems
--------------------
chkrootkit has been tested on: Linux 2.0.x, 2.2.x, 2.4.x and 2.6.x,
FreeBSD 2.2.x, 3.x, 4.x and 5.x, OpenBSD 2.x and 3.x., NetBSD 1.6.x,
Solaris 2.5.1, 2.6, 8.0 and 9.0, HP-UX 11, Tru64, BSDI and Mac OS X.
4. Package Contents
-------------------
README
README.chklastlog
README.chkwtmp
COPYRIGHT
chkrootkit.lsm
Makefile
chklastlog.c
chkproc.c
chkdirs.c
chkwtmp.c
check_wtmpx.c
ifpromisc.c
strings.c
chkutmp.c
chkrootkit
5. Installation
---------------
To compile the C programs type:
# make sense
After that it is ready to use and you can simply type:
# ./chkrootkit
6. Usage
--------
chkrootkit must run as root. The simplest way is:
# ./chkrootkit
This will perform all tests. You can also specify only the tests you
want, as shown below:
Usage: ./chkrootkit [options] [testname ...]
Options:
-h show this help and exit
-V show version information and exit
-l show available tests
-d debug
-q quiet mode
-x expert mode
-r dir use dir as the root directory
-p dir1:dir2:dirN path for the external commands used by chkrootkit
-n skip NFS mounted dirs
Where testname stands for one or more from the following list:
aliens asp bindshell lkm rexedcs sniffer w55808 wted scalper slapper
z2 chkutmp amd basename biff chfn chsh cron crontab date du dirname
echo egrep env find fingerd gpm grep hdparm su ifconfig inetd
inetdconf identd init killall ldsopreload login ls lsof mail mingetty
netstat named passwd pidof pop2 pop3 ps pstree rpcinfo rlogind rshd
slogin sendmail sshd syslogd tar tcpd tcpdump top telnetd timed
traceroute vdir w write
For example, the following command checks for trojaned ps and ls
binaries and also checks if the network interface is in promiscuous
mode.
# ./chkrootkit ps ls sniffer
The `-q' option can be used to put chkrootkit in quiet mode -- in
this mode only output messages with `infected' status are shown.
With the `-x' option the user can examine suspicious strings in the
binary programs that may indicate a trojan -- all the analysis is
left to the user.
Lots of data can be seen with:
# ./chkrootkit -x | more
Pathnames inside system commands:
# ./chkrootkit -x | egrep '^/'
chkrootkit uses the following commands to make its tests: awk, cut,
egrep, find, head, id, ls, netstat, ps, strings, sed, uname. It is
possible, with the `-p' option, to supply an alternate path to
chkrootkit so it won't use the system's (possibly) compromised
binaries to make its tests.
To use, for example, binaries in /cdrom/bin:
# ./chkrootkit -p /cdrom/bin
It is possible to add more paths with a `:'
# ./chkrootkit -p /cdrom/bin:/floppy/mybin
Sometimes is a good idea to mount the disk from a compromised machine
on a machine you trust. Just mount the disk and specify a new
rootdir with the `-r' option.
For example, suppose the disk you want to check is mounted under
/mnt, then:
# ./chkrootkit -r /mnt
7. Output Messages
------------------
The following messages are printed by chkrootkit (except with the -x
and -q command options) during its tests:
"INFECTED": the test has identified a command probably modified by
a known rootkit;
"not infected": the test didn't find any known rootkit signature.
"not tested": the test was not performed -- this could happen in
the following situations:
a) the test is OS specific;
b) the test depends on an external program that is not available;
c) some specific command line options are given. (e.g. -r ).
"not found": the command to be tested is not available;
"Vulnerable but disabled": the command is infected but not in use.
(not running or commented in inetd.conf)
8. A trojaned command has been found. What should I do now?
------------------------------------------------------------
Your biggest problem is that your machine has been compromised and
this bad guy has root privileges.
Maybe you can solve the problem by just replacing the trojaned
command -- the best way is to reinstall the machine from a safe media
and to follow your vendor's security recommendations.
9. Reports and questions
------------------------
Please send comments, questions and bug reports to
and .
A simple FAQ and Related information about rootkits and security can
be found at chkrootkit's homepage, .
10. ACKNOWLEDGMENTS
-------------------
See the ACKNOWLEDGMENTS file.
11. ChangeLog
-------------
02/20/1997 - Initial release
02/25/1997 - Version 0.4, formal testing.
03/30/1997 - Version 0.5, suspect files routine added.
06/11/1997 - Version 0.6, minor fixes and Debian compatibility.
06/24/1997 - Version 0.7, FreeBSD compatibility fixed.
08/07/1997 - Version 0.8, yet another FreeBSD compatibility and
RedHat PAM fixed.
04/02/1998 - Version 0.9, new r00tkits versions support.
07/03/1998 - Version 0.10, another types of r00tkits supported.
10/15/1998 - Version 0.11, bug found by Alberto Courrege Gomide fixed.
11/30/1998 - Version 0.12, lrk4 support added.
12/26/1998 - Version 0.13, minor fixes for Red Hat and glibc users.
06/14/1999 - Version 0.14, Sun/Solaris initial support added.
04/29/2000 - Version 0.15, lrk5 features added and minor fixes.
07/09/2000 - Version 0.16, new r00tkits types support and contrib patches.
09/16/2000 - Version 0.17, more contrib patches, rootkit types and
Loadable Kernel Modules (LKM) trojan checking
added.
10/08/2000 - Version 0.18, new rookits types support and many bug fixes.
12/24/2000 - Version 0.19, -r, -p, -l options added. ARK support
added. Some bug fixes.
01/18/2001 - Version 0.20, Ramen Worm and latest t0rnkit detection,
temporay check for promisc mode disabled
on Solaris boxes.
01/19/2001 - Version 0.21, Corrects a bug in the Ramen Worm detection.
01/26/2001 - Version 0.22, chklastlog core dump bug fixed, login and
bindshell false positives fixed, cron test
improvement.
03/12/2001 - Version 0.23, lrk6, rh[67]-shaper, RSHA and Romanian
rootkit detection. Test for shell history
file anomalies. More ports added to the
bindshell test.
03/15/2001 - Version 0.23a fixes a bug found in the cron and
bindshell tests.
03/22/2001 - Version 0.30 lots of new tests added. RK17 and Lion
Worm detection.
04/07/2001 - Version 0.31 new tests: gpm, rlogind, mgetty. Adore
Worm detection. Some bug fixes.
05/07/2001 - Version 0.32 t0rn v8, LPD Worm, kenny-rk and Adore LKM
detection. Some Solaris bug fixes.
06/02/2001 - Version 0.33 new tests added. ShitC, Omega and Wormkit
Worm detection. dsc-rootkit detection.
Some bug fixes.
09/19/2001 - Version 0.34 new tests added. check_wtmpx.c added.
Ducoci rootkit and x.c Worm detection.
`-q' option added.
01/17/2002 - Version 0.35 tests added: lsof and ldsopreload.
strings.c added. Ports added to the
bindshell test. RST.b, duarawkz, knark
LKM, Monkit, Hidrootkit, Bobkit, Pizdakit,
t0rn v8.0 (variant) detection.
06/15/2002 - Version 0.36 test added: w. chkproc.c additions.
Showtee, Optickit, T.R.K, MithRa's
Rootkit, George and SucKIT detection.
09/16/2002 - Version 0.37 tests added: scalper and slapper.
Scalper Worm, Slapper Worm, OpenBSD rk
v1, Illogic and SK rootkit detection.
chklastlog.c and chkproc.c improvements.
Small chkrootkit bug fix.
12/20/2002 - Version 0.38 chkdirs.c added. chkproc.c improvements.
slapper B, sebek LKM, LOC, Romanian
rootkit detection. new test added: trojan
tcpdump. Minor bug fixes in the
chkrootkit script.
01/30/2003 - Version 0.39 chkdirs.c and chkproc.c fixes. bug fixes
in the chkrootkit script. (more) Slapper
variants detection.
04/03/2003 - Version 0.40 chkproc.c fixes. Tru64 support. small
corrections in chkrootkit. New test
added: init. New rootkits detected: shv4,
Aquatica, ZK.
06/20/2003 - Version 0.41 chkproc.c fixes. New test added: vdir.
New worms detected: 55808.A and TC2. New
rootkits detected: Volc, Gold2, Anonoying,
Suckit (improved), ZK (improved). Minor
corrections.
09/12/2003 - Version 0.42 BSDI support for chkdirs.c. chkproc.c
fix. New rootkit detected: ShKit.
ifpromisc test fixed for Linux 2.4.x
kernels. corrections for the -r option.
FreeBSD 5.x support. HPUX correction.
Extra "\n" removed from chklastlog.c
output.
09/18/2003 - Version 0.42a Bug fix release.
09/20/2003 - Version 0.42b Bug fix release.
12/27/2003 - Version 0.43 C++ comments removed from chkproc.c. New
rootkits detected: AjaKit and zaRwT. New
CGI backdoors detected. ifpromisc.c:
better detection of promisc mode on newer
Linux kernels. New command line option
(-n) to skip NFS mounted dirs. Minor bug
corrections.
09/01/2004 - Version 0.44 chkwtmp.c: del counter fixed. chkproc.c:
better support for Linux threads. New
rootkit detected: Madalin. Lots of minor
bug fixes.
02/22/2005 - Version 0.45 chkproc.c: better support for Linux
threads. New rootkit detected: Fu,
Kenga3, ESRK. New test: chkutmp. -n
option improvement. Minor bug fixes.
10/26/2005 - Version 0.46 chkproc.c: more fixes to better support
Linux threads. chkutmp.c: improved
execution speed. chkwtmp.c: segfault
fixed. New rootkit detected: rootedoor.
Mac OS X support added. Minor bug fixes.
10/28/2005 - Version 0.46a chkproc.c: bug fix for FreeBSD: chkproc
was sending a SIGXFSZ (kill -25) to init,
causing a reboot.
10/10/2006 - Version 0.47 chkproc.c: bug fixes, use of getpriority(),
Enye LKM detected. chkrootkit: crontab
test, Enye LKM and Lupper.Worm detected,
minor bug fixes.
-------------- Thx for using chkrootkit ----------------
