Rocky Linux8.6 : SNORT ,Tripwire ,Chkrootkit

2022.06.08

Install SNORT

1.advance preparation

①Add the CodeReady Red Hat repository and install the required software

# dnf config-manager --set-enabled powertools
# dnf -y install bison flex libtool nghttp2 libnghttp2-devel \
libpcap-devel pcre-devel openssl-devel libdnet-devel \
libtirpc-devel git gcc-c++ libunwind-devel cmake hwloc-devel \
luajit-devel xz-devel libnfnetlink-devel libmnl-devel \
libnetfilter_queue-devel uuid-devel libsafec-devel
②Install DAQ
# mkdir /var/src
# cd /var/src
# wget https://snort.org/downloads/snort/daq-2.0.7.tar.gz
# tar zxvf daq-2.0.7.tar.gz
# cd daq-2.0.7
# autoreconf -f -i
# ./configure
# make
# make install
③Install Lua
# cd /var/src
# wget http://luajit.org/download/LuaJIT-2.0.5.tar.gz
# tar -zxvf LuaJIT-2.0.5.tar.gz
# cd LuaJIT-2.0.5
# make
# make install
④Create fake release files
# /bin/cat << EOT >/etc/fedora-release
Fedora release 28 (Rawhide)
EOT

2. Download, compile, and install Snort

# cd /var/src
# wget https://snort.org/downloads/archive/snort/snort-2.9.18.1.tar.gz
# tar -zxvf snort-2.9.18.1.tar.gz
# cd snort-2.9.18.1
# ./configure --enable-sourcefire
# make
# make install
# ldconfig
# ln -s /usr/local/bin/snort /usr/sbin/snort
Delete fake release files
# rm /etc/fedora-release

3.Create groups and users, necessary directories and files

# groupadd snort
# useradd snort -r -s /sbin/nologin -c SNORT_IDS -g snort

# mkdir /etc/snort
# mkdir -p /etc/snort/rules
# mkdir /var/log/snort
# mkdir /usr/local/lib/snort_dynamicrules
# mkdir /etc/snort/preproc_rules

# chmod -R 5775 /etc/snort
# chmod -R 5775 /var/log/snort
# chmod -R 5775 /usr/local/lib/snort_dynamicrules
# chown -R snort:snort /etc/snort
# chown -R snort:snort /var/log/snort
# chown -R snort:snort /usr/local/lib/snort_dynamicrules

Create the following files
# touch /etc/snort/rules/white_list.rules
# touch /etc/snort/rules/black_list.rules
# touch /etc/snort/rules/local.rules

Setup configuration files... Copy all files to the configuration directory.

# cp /var/src/snort-2.9.18.1/etc/*.conf* /etc/snort
# cp /var/src/snort-2.9.18.1/etc/*.map* /etc/snort

4.Use of Community Rules

①Get Community Rules

# wget https://www.snort.org/rules/community -O ~/community.tar.gz
②Extract rules and copy to configuration folder
# tar -xvf ~/community.tar.gz -C ~/
# cp ~/community-rules/* /etc/snort/rules
There are various rule files that are not included in the community rules.
Use the sed command to comment out unnecessary lines.
# sed -i 's/include \$RULE\_PATH/#include \$RULE\_PATH/' /etc/snort/snort.conf

5. Retrieving Registered User Rules

Once registered on the Snort website, you can use your Oink code to download registered user rules; the Oink code is located in your Snort user account details.
Replace oinkcode with your personal code in the following command
# wget https://www.snort.org/rules/snortrules-snapshot-29181.tar.gz?oinkcode=<oink-code> -O ~/registered.tar.gz

Once download is complete, extract rules to the configuration directory

# tar -xvf ~/registered.tar.gz -C /etc/snort

6. Network and Rule Configuration

# vi /etc/snort/snort.conf
●Line 45
# Setup the network addresses you are protecting
ipvar HOME_NET 192.168.11.0/24　←adapt to one's environment
●Line 48
# Set up the external network addresses. Leave as "any" in most situations
ipvar EXTERNAL_NET !$HOME_NET
●Line 104-106 :　Comment out and add below
# Path to your rules files (this can be a relative path)
# var RULE_PATH ../rules
# var SO_RULE_PATH ../so_rules
# var PREPROC_RULE_PATH ../preproc_rules
var RULE_PATH /etc/snort/rules
var SO_RULE_PATH /etc/snort/so_rules
var PREPROC_RULE_PATH /etc/snort/preproc_rules
●Per line 116 : Comment out and add below
# Set the absolute path appropriately
#var WHITE_LIST_PATH ../rules
#var BLACK_LIST_PATH ../rules
var WHITE_LIST_PATH /etc/snort/rules
var BLACK_LIST_PATH /etc/snort/rules
●Per line 525 : add
# unified2
# Recommended for most installs
output unified2: filename snort.log, limit 128
●Per line 550 : To make custom rules readable, local.rules must be uncommented
include $RULE_PATH/local.rules
●If you are using community rules, also add the following line just below the local.rules line, for example
include $RULE_PATH/community.rules

7. Verification of settings

Use parameter -T to test configuration and enable test mode

# snort -T -c /etc/snort/rules/snort.conf

MaxRss at the end of detection rules:809420

--== Initialization Complete ==--

,,_       -*> Snort! <*-
o" )~    Version 2.9.18.1 GRE (Build 1005)
''''       By Martin Roesch & The Snort Team: http://www.snort.org/contact#team
Copyright (C) 2014-2021 Cisco and/or its affiliates. All rights reserved.
Copyright (C) 1998-2013 Sourcefire, Inc., et al.
Using libpcap version 1.9.1 (with TPACKET_V3)
Using PCRE version: 8.45 2021-06-15
Using ZLIB version: 1.2.11

Rules Engine: SF_SNORT_DETECTION_ENGINE Version 3.2 <Build 1>
Preprocessor Object: SF_DNS Version 1.1 <Build 4>
Preprocessor Object: appid Version 1.1 <Build 5>
Preprocessor Object: SF_S7COMMPLUS Version 1.0 <Build 1>
Preprocessor Object: SF_FTPTELNET Version 1.2 <Build 13>
Preprocessor Object: SF_POP Version 1.0 <Build 1>
Preprocessor Object: SF_SSLPP Version 1.1 <Build 4>

Total snort Fixed Memory Cost - MaxRss:809420
Snort successfully validated the configuration!
Snort exiting

If an error occurs, copy the corresponding file to /etc/snort/rules
In our case, the error occurred in the following file
# cp /var/src/snort-2.9.18.1/etc/classification.config /etc/snort/rules
cp /var/src/snort-2.9.18.1/etc/reference.config /etc/snort/rules
cp /var/src/snort-2.9.18.1/etc/threshold.conf /etc/snort/rules
cp /var/src/snort-2.9.18.1/etc/unicode.map /etc/snort/rules/
If you get a unicode.map error
# cp /usr/local/src/snort-2.9.18.1/etc/unicode.map /etc/snort/rules
Also, if you get the error "/etc/snort/rules/snort.conf(322) => Invalid keyword '}'".
decompress_swf { deflate lzma } \　　Comment.
# decompress_swf { deflate lzma } \

8. Configuration Testing

①To test if Snort is logging alerts, add custom detection rule alerts for incoming ICMP connections to the local.rules file.
# vi /etc/snort/rules/local.rules
●Add the following line to the last line
alert icmp any any -> $HOME_NET any (msg:"ICMP test"; sid:10000001; rev:001;)
②Start Snort at the console and output an alert to stdout. The correct network interface (e.g. eth0) must be selected

# snort -A console -i eth0 -u snort -g snort -c /etc/snort/snort.conf

With Snort up and running, ping from another computer; you will see the following notification for each ICMP call in the terminal where Snort is running
Commencing packet processing (pid=39776)
06/13-10:19:56.262263 [**] [1:10000001:1] ICMP test [**] [Priority: 0] {ICMP} 192.168.11.20 -> 192.168.11.83
06/13-10:19:56.262316 [**] [1:10000001:1] ICMP test [**] [Priority: 0] {ICMP} 192.168.11.83 -> 192.168.11.20
06/13-10:19:57.267099 [**] [1:10000001:1] ICMP test [**] [Priority: 0] {ICMP} 192.168.11.20 -> 192.168.11.83
06/13-10:19:57.267145 [**] [1:10000001:1] ICMP test [**] [Priority: 0] {ICMP} 192.168.11.83 -> 192.168.11.20
06/13-10:19:58.272613 [**] [1:10000001:1] ICMP test [**] [Priority: 0] {ICMP} 192.168.11.20 -> 192.168.11.83
06/13-10:19:58.272657 [**] [1:10000001:1] ICMP test [**] [Priority: 0] {ICMP} 192.168.11.83 -> 192.168.11.20
06/13-10:19:59.277961 [**] [1:10000001:1] ICMP test [**] [Priority: 0] {ICMP} 192.168.11.20 -> 192.168.11.83
06/13-10:19:59.278005 [**] [1:10000001:1] ICMP test [**] [Priority: 0] {ICMP} 192.168.11.83 -> 192.168.11.20

9. Running Snort in the background

①Create a startup script for Snort

# vi /lib/systemd/system/snort.service

[Unit]

Description=Snort NIDS Daemon
After=syslog.target network.target

[Service]

Type=simple
ExecStart=/usr/local/bin/snort -q -u snort -g snort -c /etc/snort/snort.conf -i eth0

[Install]

WantedBy=multi-user.target

②After defining the service, reload and run the systemctl daemon

# systemctl daemon-reload
# systemctl start snort

Install Tripwire

1.Download and installation

# cd /usr/local/src
# wget https://rpmfind.net/linux/epel/8/Everything/x86_64/Packages/t/tripwire-2.4.3.7-5.el8.x86_64.rpm
# rpm -Uvh tripwire-2.4.3.7-5.el8.x86_64.rpm

2.Set passphrase

Set site passphrase and local passphrase

# tripwire-setup-keyfiles
----------------------------------------------
The Tripwire site and local passphrases are used to sign a variety of
files, such as the configuration, policy, and database files.
Passphrases should be at least 8 characters in length and contain both
letters and numbers.
See the Tripwire manual for more information.
----------------------------------------------
Creating key files...
(When selecting a passphrase, keep in mind that good passphrases typically
have upper and lower case letters, digits and punctuation marks, and are
at least 8 characters in length.)
Enter the site keyfile passphrase: ←Enter any "Site Passphrase"
Verify the site keyfile passphrase: ←Enter "Site Passphrase" again
Generating key (this may take several minutes)...Key generation complete.
(When selecting a passphrase, keep in mind that good passphrases typically
have upper and lower case letters, digits and punctuation marks, and are
at least 8 characters in length.)
Enter the local keyfile passphrase: ←Enter any "local passphrase
Verify the local keyfile passphrase: ←Enter "Local Passphrase" again
Generating key (this may take several minutes)...Key generation complete.
----------------------------------------------
Signing configuration file...
Please enter your site passphrase: ←Enter "Site Passphrase"
Wrote configuration file: /etc/tripwire/tw.cfg
A clear-text version of the Tripwire configuration file:
/etc/tripwire/twcfg.txt
has been preserved for your inspection. It is recommended that you
move this file to a secure location and/or encrypt it in place (using a
tool such as GPG, for example) after you have examined it.
----------------------------------------------
Signing policy file...
Please enter your site passphrase: ←Enter "Site Passphrase"
Wrote policy file: /etc/tripwire/tw.pol
A clear-text version of the Tripwire policy file:
/etc/tripwire/twpol.txt
～中略～
default values from the current configuration file are used.

3.Tripwire Configuration

①Configuration File Editing

# vi /etc/tripwire/twcfg.txt
●Line 9
Add "#" at the beginning of the line and "LOOSEDIRECTORYCHECKING =true" on the line below it
●Line 12
Add "#" at the beginning of the line and "REPORTLEVEL =4" on the line below it.
#REPORTLEVEL =3
REPORTLEVEL =4
②Create a Tripwire configuration file (cryptographically signed version)
# twadmin -m F -c /etc/tripwire/tw.cfg -S /etc/tripwire/site.key /etc/tripwire/twcfg.txt
Please enter your site passphrase: ←Enter site passphrase
Wrote configuration file: /etc/tripwire/tw.cfg
③Delete Tripwire configuration file (text version)
# rm -f /etc/tripwire/twcfg.txt
④Policy File Settings
# cd /etc/tripwire/
# vi twpolmake.pl
twpolmake.plの内容

#!/usr/bin/perl
# Tripwire Policy File customize tool
#
$POLFILE=$ARGV[0];

open(POL,"$POLFILE") or die "open error: $POLFILE" ;
my($myhost,$thost) ;
my($sharp,$tpath,$cond) ;
my($INRULE) = 0 ;

while (<POL>) {
chomp;
if (($thost) = /^HOSTNAME\s*=\s*(.*)\s*;/) {
$myhost = `hostname` ; chomp($myhost) ;
if ($thost ne $myhost) {
$_="HOSTNAME=\"$myhost\";" ;
}
}
elsif ( /^{/ ) {
$INRULE=1 ;
}
elsif ( /^}/ ) {
$INRULE=0 ;
}
elsif ($INRULE == 1 and ($sharp,$tpath,$cond) = /^(\s*\#?\s*)(\/\S+)\b(\s+->\s+.+)$/) {
$ret = ($sharp =~ s/\#//g) ;
if ($tpath eq '/sbin/e2fsadm' ) {
$cond =~ s/;\s+(tune2fs.*)$/; \#$1/ ;
}
if (! -s $tpath) {
$_ = "$sharp#$tpath$cond" if ($ret == 0) ;
}
else {
$_ = "$sharp$tpath$cond" ;
}
}
print "$_\n" ;
}
close(POL) ;

⑤policy file optimization

# perl /etc/tripwire/twpolmake.pl /etc/tripwire/twpol.txt > /etc/tripwire/twpol.txt.new
⑥Create policy file (cryptographically signed version) based on optimized policy file
# twadmin -m P -c /etc/tripwire/tw.cfg -p /etc/tripwire/tw.pol -S /etc/tripwire/site.key /etc/tripwire/twpol.txt.new
Please enter your site passphrase: ←Enter site passphrase
Wrote policy file: /etc/tripwire/tw.pol
⑦Create database and check operation
# tripwire -m i -s -c /etc/tripwire/tw.cfg
Please enter your local passphrase: ←Enter local passphrase

Create test files
# echo test > /root/test.txt
Check Tripwire operation
# tripwire -m c -s -c /etc/tripwire/tw.cfg
Delete test files
# rm -f /root/test.txt
⑧Tripwire Scheduled Scripts
# cd /var/www/system
# vi tripwire.sh
Contents of ripwire.sh

#!/bin/bash

PATH=/usr/sbin:/usr/bin:/bin:/usr/local/tripwire/sbin

# Passphrase setting
LOCALPASS= ←local passphrase
SITEPASS= 　←site passphrase

cd /etc/tripwire

# Tripwire check run
tripwire -m c -s -c tw.cfg|mail -s "Tripwire(R) Integrity Check Report in `hostname`" root

# Policy File Update
twadmin -m p -c tw.cfg -p tw.pol -S site.key > twpol.txt
perl twpolmake.pl twpol.txt > twpol.txt.new
twadmin -m P -c tw.cfg -p tw.pol -S site.key -Q $SITEPASS twpol.txt.new > /dev/null
rm -f twpol.txt* *.bak

# Database modernization
rm -f /usr/local/tripwire/lib/tripwire/*.twd*
tripwire -m i -s -c tw.cfg -P $LOCALPASS

⑨Tripwire Autorun Script Execution Settings

# chmod 700 tripwire.sh

Add to cron
# crontab -e
0 3 * * * /var/www/system/tripwire.sh

Reference: Script for reporting results by e-mail

#!/bin/bash

PATH=/usr/sbin:/usr/bin:/bin:/usr/local/tripwire/sbin

# Passphrase setting
LOCALPASS=xxxxx # local key passphrase
SITEPASS=xxxxx # site key passphrase

#Email Address for Notification
MAIL="<your mailaddress> "

cd /etc/tripwire

# Tripwire check run
tripwire -m c -s -c tw.cfg|mail -s "Tripwire(R) Integrity Check Report in `hostname`" $MAIL

# Policy File Update
twadmin -m p -c tw.cfg -p tw.pol -S site.key > twpol.txt
perl twpolmake.pl twpol.txt > twpol.txt.new
twadmin -m P -c tw.cfg -p tw.pol -S site.key -Q $SITEPASS twpol.txt.new > /dev/null
rm -f twpol.txt* *.bak

# Database modernization
rm -f /usr/local/tripwire/lib/tripwire/*.twd*
tripwire -m i -s -c tw.cfg -P $LOCALPASS

Install Chkrootkit

①Download and install chkrootkit

# cd /usr/local/src
# wget https://launchpad.net/chkrootkit/main/0.55/+download/chkrootkit-0.55.tar.gz
# tar xvf chkrootkit-0.55.tar.gz

➁Create /root/bin directory and move chkrootkit command to that directory
# mkdir -p /root/bin
# mv chkrootkit-0.55/chkrootkit /root/bin
➂Check chkrootkit.
# chkrootkit | grep INFECTED
If nothing is displayed, no problem.
Searching for Linux.Xor.DDoS ... INFECTED: Possible Malicious Linux.Xor.DDoS installed
If the above appears
It seems that you are just raising a file with execute permissions in /tmp, so I'll consider it a false positive.
For now, in our case, we have made the following files unexecutable
# chmod -x ks-script-ha_lzbh5 ks-script-uu6cvhzn
④Create chkrootkit periodic execution script and change permissions

Create chkrootkit execution script in a directory where it is automatically executed daily
# vi /etc/cron.daily/chkrootkit

Scheduled Script Contents

#!/bin/bash

PATH=/usr/bin:/bin:/root/bin

LOG=/tmp/$(basename ${0})

# Execute chkrootkit
chkrootkit > $LOG 2>&1

# log output
cat $LOG | logger -t $(basename ${0})

# SMTPSのbindshell誤検知対応
if [ ! -z "$(grep 465 $LOG)" ] && \
[ -z $(/usr/sbin/lsof -i:465|grep bindshell) ]; then
sed -i '/465/d' $LOG
fi
if [ ! -z "$(grep Suckit $LOG)" ] && \
[ -z "$(rpm -V `rpm -qf /sbin/init`)" ]; then
sed -i '/Suckit/d' $LOG
fi

# Send mail to root only when rootkit is detected
[ ! -z "$(grep INFECTED $LOG)" ] && \
grep INFECTED $LOG | mail -s "chkrootkit report in `hostname`" root

Add execution permission to chkrootkit execution script
# chmod 700 /etc/cron.daily/chkrootkit
⑥Backup commands used by chkrootkit
If the commands used by chkrootkit are tampered with, rootkit will not be detected.
Back up these commands.
If necessary, run chkrootkit with the backed up command
# cd /root
# mkdir /root/chkrootkit_cmd
# cp `which --skip-alias awk cut echo egrep find head id ls netstat ps strings sed ssh uname` chkrootkit_cmd/
# ls -l /root/chkrootkit_cmd/
total 2484
-rwxr-xr-x 1 root root 685712 Jun 13 11:08 awk
-rwxr-xr-x 1 root root 50840 Jun 13 11:08 cut
-rwxr-xr-x 1 root root 38376 Jun 13 11:08 echo
-rwxr-xr-x 1 root root 28 Jun 13 11:08 egrep
-rwxr-xr-x 1 root root 228856 Jun 13 11:08 find
-rwxr-xr-x 1 root root 46736 Jun 13 11:08 head
-rwxr-xr-x 1 root root 46672 Jun 13 11:08 id
-rwxr-xr-x 1 root root 143400 Jun 13 11:08 ls
-rwxr-xr-x 1 root root 162432 Jun 13 11:08 netstat
-rwxr-xr-x 1 root root 138096 Jun 13 11:08 ps
-rwxr-xr-x 1 root root 118024 Jun 13 11:08 sed
-rwxr-xr-x 1 root root 775632 Jun 13 11:08 ssh
-rwxr-xr-x 1 root root 38320 Jun 13 11:08 strings
-rwxr-xr-x 1 root root 38392 Jun 13 11:08 uname
⑦Run chkrootkit on the copied command
# chkrootkit -p /root/chkrootkit_cmd | grep INFECTED
If nothing is displayed, no problem.
⑧Compresses backed up commands
# tar zcvf chkrootkit_cmd.tar.gz chkrootkit_cmd
chkrootkit_cmd/
chkrootkit_cmd/awk
chkrootkit_cmd/cut
chkrootkit_cmd/echo
chkrootkit_cmd/egrep
chkrootkit_cmd/find
chkrootkit_cmd/head
chkrootkit_cmd/id
chkrootkit_cmd/ls
chkrootkit_cmd/netstat
chkrootkit_cmd/ps
chkrootkit_cmd/strings
chkrootkit_cmd/sed
chkrootkit_cmd/ssh
chkrootkit_cmd/uname
# ls -l
total 93924
-rw-------. 1 root root 1460 Jun 11 13:35 anaconda-ks.cfg
drwxr-xr-x 2 root root 24 Jun 13 10:52 bin
drwxr-xr-x 2 root root 172 Jun 13 11:08 chkrootkit_cmd
-rw-r--r-- 1 root root 1161551 Jun 13 11:10 chkrootkit_cmd.tar.gz
⑨Send chkrootkit use command (compressed version) to root by e-mail
# echo|mail -a chkrootkit_cmd.tar.gz -s chkrootkit_cmd.tar.gz root
⑩Download and save chkrootkit_cmd.tar.gz file to Windows
⑪Delete commands on the backed up server
# rm -f chkrootkit_cmd.tar.gz
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