Install Tripwire Intrusion Detection System (IDS) on Linux

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Tripwire is an open-source security and data integrity tool useful for monitoring and alerting on specific file change(s) on a range of systems. If any file gets modified or changed, it will send a alert to you. If the changes are valid, the you can accept the changes by updating the tripwire database.

Install Tripwire

On Ubuntu/Debian:

sk@sk:~$ sudo apt-get install tripwire

sk@sk: ~_001

Select Internet site and Enter.

sk@sk: ~_002

Enter the mail (FQDN) name.

sk@sk: ~_003

Now the Tripwire configuration task starts.

sk@sk: ~_004

Select Yes to create site key pass phrases.

sk@sk: ~_005

Select yes to rebuild the Tripwire configuration file.

sk@sk: ~_008

Rebuild Tripwire policy file. Select Yes.

sk@sk: ~_009

Enter site-key passphrase.

sk@sk: ~_010

Re-enter site-key passphrase.

sk@sk: ~_011

Enter local key passphrase.

sk@sk: ~_012

Re-enter passphrase.

sk@sk: ~_013

Now the Tripwire has been installed with local and site key passphrases.

sk@sk: ~_014

On CentOS/RHEL, Tripwire will not be found on official repository. So add EPEL repository to install Tripwire:

[root@server ~]# rpm -ivh http://dl.fedoraproject.org/pub/epel/6/i386/epel-release-6-8.noarch.rpm

Now install Tripwire:

[root@server ~]# yum install tripwire -y

Create keyfile pass phrases

Likewise in Ubuntu local and site keyfile passphrases will not be created when installing Tripwire. Enter the following commands to create site and local keyfile pass phrases for Tripwire:

[root@server ~]# 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:   

Verify the site keyfile passphrase:

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:

Verify the local keyfile passphrase:

Generating key (this may take several minutes)...Key generation complete.

----------------------------------------------

Signing configuration file...

Please enter your 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: 

Wrote policy file: /etc/tripwire/tw.pol

A clear-text version of the Tripwire policy file:

/etc/tripwire/twpol.txt

has been preserved for your inspection. This implements a minimal

policy, intended only to test essential Tripwire functionality. You

should edit the policy file to describe your system, and then use

twadmin to generate a new signed copy of the Tripwire policy.

Once you have a satisfactory Tripwire policy file, you should move the

clear-text version to a secure location and/or encrypt it in place

(using a tool such as GPG, for example).

Now run "tripwire --init" to enter Database Initialization Mode. This

reads the policy file, generates a database based on its contents, and

then cryptographically signs the resulting database. Options can be

entered on the command line to specify which policy, configuration, and

key files are used to create the database. The filename for the

database can be specified as well. If no options are specified, the

default values from the current configuration file are used.

Initialize Tripwire Database

On Ubuntu/Debian:

sk@sk:~$ sudo tripwire --init
Please enter your local passphrase: 
Parsing policy file: /etc/tripwire/tw.pol
Generating the database...
*** Processing Unix File System ***

### Warning: File system error.

### Filename: /var/lib/tripwire/sk.twd

### No such file or directory

### Continuing...

### Warning: File system error.

### Filename: /etc/rc.boot

### No such file or directory

[...]

### Continuing...

The object: "/proc/sys/fs/binfmt_misc" is on a different file system...ignoring.

Wrote database file: /var/lib/tripwire/sk.twd

The database was successfully generated.

On CentOS/RHEL:

[root@server ~]# tripwire --init
Please enter your local passphrase: 
Parsing policy file: /etc/tripwire/tw.pol
Generating the database...
*** Processing Unix File System ***
### Warning: File system error.
### Filename: /dev/kmem
### No such file or directory
### Continuing...
[...]

### Continuing...

Wrote database file: /var/lib/tripwire/server.unixmen.com.twd

The database was successfully generated.

In the both above outputs, you may notice that a error called “No such file or Directory” and “file system error”. This is because the tripwire scans every files/directories which are mentioned in the tripwire configuration file. The files/directories might not be existed in your system. Comment the lines which are showing this error in the tripwire config file or leave it as is.

To do that open the file /etc/tripwire/twpol.txt and comment the file/directory lines which are not present in your system.

On Ubuntu/Debian:

sk@sk:~$ sudo vi /etc/tripwire/twpol.txt 

On CentOS/RHEL:

[root@server ~]# vi /etc/tripwire/twpol.txt 

Find and comment the lines which are showing error. Save and close the file.

Testing Tripwire

Let us add a file called unixmen to see how Tripwire IDS works.

[root@server ~]# touch unixmen

Now run the Tripwire interactive command.

[root@server ~]# tripwire --check --interactive

Once you run this command, tripwire will collect all the files/directories changes/modifications and automatically open the result in the vi editor.

This is how your output looks:

Open Source Tripwire(R) 2.4.1 Integrity Check Report

Report generated by: root

Report created on: Friday 21 June 2013 02:05:02 PM IST

Database last updated on: Never

===============================================================================

Report Summary:

===============================================================================

Host name: server.unixmen.com

Host IP address: Unknown IP

Host ID: None

Policy file used: /etc/tripwire/tw.pol

Configuration file used: /etc/tripwire/tw.cfg

Database file used: /var/lib/tripwire/server.unixmen.com.twd

Command line used: tripwire --check --interactive

===============================================================================

Rule Summary:

[...]

Scroll down through the file and it will show a notification that a new file called unixmen have been added:

[...]

Remove the "x" from the adjacent box to prevent updating the database

with the new values for this object.

Added:

[x] "/root/unixmen"

Modified:

[x] "/root"

[...]

-------------------------------------------------------------------------------

*** End of report ***

Open Source Tripwire 2.4 Portions copyright 2000 Tripwire, Inc. Tripwire is a registered

trademark of Tripwire, Inc. This software comes with ABSOLUTELY NO WARRANTY;

for details use --version. This is free software which may be redistributed

or modified only under certain conditions; see COPYING for details.

All rights reserved.

If this is a valid, you can accept the changes by updating the Tripwire database. Or just remove the x mark and update database. Type :q to save and exit from the file. It will ask the local passphrase, enter the passphrase. Now the tripwire database has been updated.

View Tripwire report files

Normally Tripwire report file is stored under /var/lib/tripwire/report/ directory with extension .twr. You can’t view this type of files using any editor. First you have to convert the files to txt file. To do that enter the following command in the terminal:

[root@server ~]# twprint --print-report --twrfile /var/lib/tripwire/report/server.unixmen.com-20130621-141518.twr > /tmp/tripwire_report.txt

Now open it using your favorite editor:

[root@server ~]# vi /tmp/tripwire_report.txt

Note: Report is not encrypted.

Open Source Tripwire(R) 2.4.1 Integrity Check Report

Report generated by: root

Report created on: Friday 21 June 2013 02:15:18 PM IST

Database last updated on: Never

==============================================================================

Report Summary:

================================================================
==============

Host name: server.unixmen.com

Host IP address: Unknown IP

Host ID: None

Policy file used: /etc/tripwire/tw.pol

Configuration file used: /etc/tripwire/tw.cfg

Database file used: /var/lib/tripwire/server.unixmen.com.twd

Command line used: tripwire --check --interactive

===============================================================================

Rule Summary:

======================================

[...]

To view the Tripwire configuration location:

[root@server ~]# twadmin --print-cfgfile
ROOT =/usr/sbin
POLFILE =/etc/tripwire/tw.pol
DBFILE =/var/lib/tripwire/$(HOSTNAME).twd
REPORTFILE =/var/lib/tripwire/report/$(HOSTNAME)-$(DATE).twr
SITEKEYFILE =/etc/tripwire/site.key
LOCALKEYFILE =/etc/tripwire/$(HOSTNAME)-local.key
EDITOR =/bin/vi
LATEPROMPTING =false
LOOSEDIRECTORYCHECKING =false
MAILNOVIOLATIONS =true
EMAILREPORTLEVEL =3
REPORTLEVEL =3
MAILMETHOD =SENDMAIL
SYSLOGREPORTING =false
MAILPROGRAM =/usr/sbin/sendmail -oi -t

To view the Policy file location:

[root@server ~]# twadmin --print-polfile

Schedule Tripwire check Using Cron

Open the /etc/crontab file and append the lines as shown below:

[root@server ~]# vi /etc/crontab

00 12 * * * /usr/sbin/tripwire --check

The above command will execute Tripwire check daily at 12′o clock.

For questions please refer to our Q/A forum at : http://ask.unixmen.com/


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