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Rootkit Hunter

April 22, 2020

rkhunter

rkhunter (Rootkit Hunter) is a security monitoring tool written in Bash for POSIX compliant systems. It carries out various checks for rootkits, backdoors, and local exploits. It compares hashes of important files with known good ones, searching for default directories of rootkits, wrong permissions, hidden files, and suspicious strings in kernel modules. rkhunter can run on most UNIX-based systems.

Updating rkhunter

Once you have installed the latest version, run the following commands as a root user to update it.

# rkhunter --update
# rkhunter --propupd

Sample Output

# rkhunter --update
[ Rootkit Hunter version 1.4.6 ]
Checking rkhunter data files...
Checking file mirrors.dat [ No update ]
Checking file programs_bad.dat [ No update ]
Checking file backdoorports.dat [ No update ]
Checking file suspscan.dat [ No update ]
Checking file i18n/cn [ No update ]
Checking file i18n/de [ No update ]
Checking file i18n/en [ No update ]
Checking file i18n/tr [ No update ]
Checking file i18n/tr.utf8 [ No update ]
Checking file i18n/zh [ No update ]
Checking file i18n/zh.utf8 [ No update ]
Checking file i18n/ja [ No update ]
# rkhunter --propupd
[ Rootkit Hunter version 1.4.6 ]
File created: searched for 177 files, found 136

Manual Scan

# rkhunter -c

Sample Output

# rkhunter -c
[ Rootkit Hunter version 1.4.6 ]
Checking system commands...
Performing 'strings' command checks
Checking 'strings' command [ OK ]
Performing 'shared libraries' checks
Checking for preloading variables [ None found ]
Checking for preloaded libraries [ None found ]
Checking LD_LIBRARY_PATH variable [ Not found ]
Performing file properties checks
Checking for prerequisites [ OK ]
/usr/sbin/adduser [ OK ]
/usr/sbin/chkconfig [ OK ]
/usr/sbin/chroot [ OK ]
/usr/sbin/depmod [ OK ]
/usr/sbin/fsck [ OK ]
/usr/sbin/fuser [ OK ]
/usr/sbin/groupadd [ OK ]
/usr/sbin/groupdel [ OK ]
/usr/sbin/groupmod [ OK ]
/usr/sbin/grpck [ OK ]
/usr/sbin/ifconfig [ OK ]
/usr/sbin/ifdown [ OK ]
/usr/sbin/ifup [ OK ]
/usr/sbin/init [ OK ]
/usr/sbin/insmod [ OK ]
/usr/sbin/ip [ OK ]
/usr/sbin/lsmod [ OK ]
/usr/sbin/modinfo [ OK ]
/usr/sbin/modprobe [ OK ]
/usr/sbin/nologin [ OK ]
/usr/sbin/ping [ OK ]
/usr/sbin/pwck [ OK ]
/usr/sbin/rmmod [ OK ]
/usr/sbin/route [ OK ]
/usr/sbin/rsyslogd [ OK ]
/usr/sbin/runlevel [ OK ]
/usr/sbin/sestatus [ OK ]
/usr/sbin/sshd [ OK ]
/usr/sbin/sulogin [ OK ]
/usr/sbin/sysctl [ OK ]
/usr/sbin/useradd [ OK ]
/usr/sbin/userdel [ OK ]
/usr/sbin/usermod [ OK ]
/usr/sbin/vipw [ OK ]
/usr/bin/awk [ OK ]
/usr/bin/basename [ OK ]
/usr/bin/bash [ OK ]
/usr/bin/cat [ OK ]
/usr/bin/chattr [ OK ]
/usr/bin/chmod [ OK ]
/usr/bin/chown [ OK ]
/usr/bin/cp [ OK ]
/usr/bin/curl [ OK ]
/usr/bin/cut [ OK ]
/usr/bin/date [ OK ]
/usr/bin/df [ OK ]
/usr/bin/diff [ OK ]
/usr/bin/dirname [ OK ]
/usr/bin/dmesg [ OK ]
/usr/bin/du [ OK ]
/usr/bin/echo [ OK ]
/usr/bin/ed [ OK ]
/usr/bin/egrep [ OK ]
/usr/bin/env [ OK ]
/usr/bin/fgrep [ OK ]
/usr/bin/file [ OK ]
/usr/bin/find [ OK ]
/usr/bin/grep [ OK ]
/usr/bin/groups [ OK ]
/usr/bin/head [ OK ]
/usr/bin/id [ OK ]
/usr/bin/ipcs [ OK ]
/usr/bin/kill [ OK ]
/usr/bin/killall [ OK ]
/usr/bin/last [ OK ]
/usr/bin/lastlog [ OK ]
/usr/bin/ldd [ OK ]
/usr/bin/less [ OK ]
/usr/bin/locate [ OK ]
/usr/bin/logger [ OK ]
/usr/bin/login [ OK ]
/usr/bin/ls [ OK ]
/usr/bin/lsattr [ OK ]
/usr/bin/lsof [ OK ]
/usr/bin/mail [ OK ]
/usr/bin/md5sum [ OK ]
/usr/bin/mktemp [ OK ]
/usr/bin/more [ OK ]
/usr/bin/mount [ OK ]
/usr/bin/mv [ OK ]
/usr/bin/netstat [ OK ]
/usr/bin/newgrp [ OK ]
/usr/bin/passwd [ OK ]
/usr/bin/perl [ OK ]
/usr/bin/pgrep [ OK ]
/usr/bin/ping [ OK ]
/usr/bin/pkill [ OK ]
/usr/bin/ps [ OK ]
/usr/bin/pstree [ OK ]
/usr/bin/pwd [ OK ]
/usr/bin/readlink [ OK ]
/usr/bin/rkhunter [ OK ]
/usr/bin/rpm [ OK ]
/usr/bin/runcon [ OK ]
/usr/bin/sed [ OK ]
/usr/bin/sh [ OK ]
/usr/bin/sha1sum [ OK ]
/usr/bin/sha224sum [ OK ]
/usr/bin/sha256sum [ OK ]
/usr/bin/sha384sum [ OK ]
/usr/bin/sha512sum [ OK ]
/usr/bin/size [ OK ]
/usr/bin/sort [ OK ]
/usr/bin/ssh [ OK ]
/usr/bin/stat [ OK ]
/usr/bin/strace [ OK ]
/usr/bin/strings [ OK ]
/usr/bin/su [ OK ]
/usr/bin/sudo [ OK ]
/usr/bin/tail [ OK ]
/usr/bin/test [ OK ]
/usr/bin/top [ OK ]
/usr/bin/touch [ OK ]
/usr/bin/tr [ OK ]
/usr/bin/uname [ OK ]
/usr/bin/uniq [ OK ]
/usr/bin/users [ OK ]
/usr/bin/vmstat [ OK ]
/usr/bin/w [ OK ]
/usr/bin/watch [ OK ]
/usr/bin/wc [ OK ]
/usr/bin/wget [ OK ]
/usr/bin/whatis [ OK ]
/usr/bin/whereis [ OK ]
/usr/bin/which [ OK ]
/usr/bin/who [ OK ]
/usr/bin/whoami [ OK ]
/usr/bin/numfmt [ OK ]
/usr/bin/kmod [ OK ]
/usr/bin/systemctl [ OK ]
/usr/bin/gawk [ OK ]
/usr/bin/mailx [ OK ]
/usr/libexec/nm-ifdown [ OK ]
/usr/libexec/nm-ifup [ OK ]
/usr/libexec/gawk [ OK ]
/usr/lib/systemd/systemd [ OK ]
[Press <ENTER> to continue]
Checking for rootkits...
Performing check of known rootkit files and directories
55808 Trojan - Variant A [ Not found ]
ADM Worm [ Not found ]
AjaKit Rootkit [ Not found ]
Adore Rootkit [ Not found ]
aPa Kit [ Not found ]
Apache Worm [ Not found ]
Ambient (ark) Rootkit [ Not found ]
Balaur Rootkit [ Not found ]
BeastKit Rootkit [ Not found ]
beX2 Rootkit [ Not found ]
BOBKit Rootkit [ Not found ]
cb Rootkit [ Not found ]
CiNIK Worm (Slapper.B variant) [ Not found ]
Danny-Boy's Abuse Kit [ Not found ]
Devil RootKit [ Not found ]
Diamorphine LKM [ Not found ]
Dica-Kit Rootkit [ Not found ]
Dreams Rootkit [ Not found ]
Duarawkz Rootkit [ Not found ]
Ebury backdoor [ Not found ]
Enye LKM [ Not found ]
Flea Linux Rootkit [ Not found ]
Fu Rootkit [ Not found ]
Fuck`it Rootkit [ Not found ]
GasKit Rootkit [ Not found ]
Heroin LKM [ Not found ]
HjC Kit [ Not found ]
ignoKit Rootkit [ Not found ]
IntoXonia-NG Rootkit [ Not found ]
Irix Rootkit [ Not found ]
Jynx Rootkit [ Not found ]
Jynx2 Rootkit [ Not found ]
KBeast Rootkit [ Not found ]
Kitko Rootkit [ Not found ]
Knark Rootkit [ Not found ]
ld-linuxv.so Rootkit [ Not found ]
Li0n Worm [ Not found ]
Lockit / LJK2 Rootkit [ Not found ]
Mokes backdoor [ Not found ]
Mood-NT Rootkit [ Not found ]
MRK Rootkit [ Not found ]
Ni0 Rootkit [ Not found ]
Ohhara Rootkit [ Not found ]
Optic Kit (Tux) Worm [ Not found ]
Oz Rootkit [ Not found ]
Phalanx Rootkit [ Not found ]
Phalanx2 Rootkit [ Not found ]
Phalanx2 Rootkit (extended tests) [ Not found ]
Portacelo Rootkit [ Not found ]
R3dstorm Toolkit [ Not found ]
RH-Sharpe's Rootkit [ Not found ]
RSHA's Rootkit [ Not found ]
Scalper Worm [ Not found ]
Sebek LKM [ Not found ]
Shutdown Rootkit [ Not found ]
SHV4 Rootkit [ Not found ]
SHV5 Rootkit [ Not found ]
Sin Rootkit [ Not found ]
Slapper Worm [ Not found ]
Sneakin Rootkit [ Not found ]
'Spanish' Rootkit [ Not found ]
Suckit Rootkit [ Not found ]
Superkit Rootkit [ Not found ]
TBD (Telnet BackDoor) [ Not found ]
TeLeKiT Rootkit [ Not found ]
T0rn Rootkit [ Not found ]
trNkit Rootkit [ Not found ]
Trojanit Kit [ Not found ]
Tuxtendo Rootkit [ Not found ]
URK Rootkit [ Not found ]
Vampire Rootkit [ Not found ]
VcKit Rootkit [ Not found ]
Volc Rootkit [ Not found ]
Xzibit Rootkit [ Not found ]
zaRwT.KiT Rootkit [ Not found ]
ZK Rootkit [ Not found ]
[Press <ENTER> to continue]
Performing additional rootkit checks
Suckit Rootkit additional checks [ OK ]
Checking for possible rootkit files and directories [ None found ]
Checking for possible rootkit strings [ None found ]
Performing malware checks
Checking running processes for suspicious files [ None found ]
Checking for hidden processes [ Skipped ]
Checking for login backdoors [ None found ]
Checking for sniffer log files [ None found ]
Checking for software intrusions [ None found ]
Checking for suspicious directories [ None found ]
Checking for Apache backdoor [ Not found ]
Performing Linux specific checks
Checking loaded kernel modules [ OK ]
Checking kernel module names [ OK ]
[Press <ENTER> to continue]
Checking the network...
Performing checks on the network ports
Checking for backdoor ports [ None found ]
Performing checks on the network interfaces
Checking for promiscuous interfaces [ None found ]
Checking the local host...
Performing system boot checks
Checking for local host name [ Found ]
Checking for system startup files [ Found ]
Checking system startup files for malware [ None found ]
Performing group and account checks
Checking for passwd file [ Found ]
Checking for root equivalent (UID 0) accounts [ None found ]
Checking for passwordless accounts [ None found ]
Checking for passwd file changes [ None found ]
Checking for group file changes [ None found ]
Checking root account shell history files [ OK ]
Performing system configuration file checks
Checking for an SSH configuration file [ Found ]
Checking if SSH root access is allowed [ Allowed ]
Checking if SSH protocol v1 is allowed [ Not set ]
Checking for other suspicious configuration settings [ None found ]
Checking for a running system logging daemon [ Found ]
Checking for a system logging configuration file [ Found ]
Checking if syslog remote logging is allowed [ Not allowed ]
Performing filesystem checks
Checking /dev for suspicious file types [ Warning ]
Checking for hidden files and directories [ None found ]
[Press <ENTER> to continue]
System checks summary
=====================
File properties checks...
Files checked: 136
Suspect files: 0
Rootkit checks...
Rootkits checked : 504
Possible rootkits: 0
Applications checks...
All checks skipped
The system checks took: 4 minutes and 17 seconds
All results have been written to the log file: /var/log/rkhunter/rkhunter.log
One or more warnings have been found while checking the system.
Please check the log file (/var/log/rkhunter/rkhunter.log)

Setting Up a Cronjob

The install of rkhunter on RHEL/CentOS creates cron jobs to run rkhunter, and to email reports to root.


Tom Person