Intrusion detection systems




Basic configuration (debian way)

Install tripwire with apt-get (apt-get install tripwire)

cd /etc/tripwire
/usr/sbin/twadmin --create-polfile twpol.txt
/usr/sbin/tripwire --init  # Have patience, this will take a minute or so and
                           # you'll get loads of "No such file" warnings...

Ok, we're fully installed now. So let's run our first check so we can tune the policy

/usr/sbin/tripwire --check > twout.txt # lots of warnings and patience  gain...

Now use this perl script (

 chmod u+x
 ./ twout.txt twpol.txt | more    # there's lots of output

fixpol prints what to do next near the end of its output in particular:

You should now run

 diff twpol.txt | more

to make sure my changes aren't garbage. If it looks ok run

 /usr/sbin/twadmin --create-polfile
 /usr/sbin/tripwire --init

to install the new policy in the database.

Now you're in a position to run

 /usr/sbin/tripwire --check

regularly in cron or whatever.

Linux (misc)

Comprehensive intrusion detection

  • tiger - Report system security vulnerabilities
  • tiger-otheros - Scripts to run Tiger in other operating systems
apt-get install tiger tiger-otheros


see also: How to scan your Linux-Distro for Root Kits

Either install the package that comes with your distribution (on Debian you would run)

apt-get install chkrootkit

or download the sources from and install manually:

wget --passive-ftp
tar xvfz chkrootkit.tar.gz
cd chkrootkit-<version>/
make sense

Afterwards, you can move the chkrootkit directory somewhere else, e.g. /usr/local/chkrootkit:

cd ..
mv chkrootkit-<version>/ /usr/local/chkrootkit

Now you can run chkrootkit manually:

cd /usr/local/chkrootkit

(if you installed a chkrootkit package coming with your distribution, your chkrootkit might be somewhere else).

You can even run chkrootkit by a cron job and get the results emailed to you: Run

crontab -e

to create a cron job like this:

0 3 * * * (cd /usr/local/chkrootkit-<version>; ./chkrootkit 2>&1 | mail -s "chkrootkit output my server"

That would run chkrootkit every night a 3.00h.


Download the latest rkhunter sources from

tar xvfz rkhunter-1.2.7.tar.gz
cd rkhunter/

This will install rkhunter to the directory /usr/local/rkhunter. Now run

rkhunter --update

to download the latest chkrootkit/trojan/worm signatures (you should do this regularly). Now you can scan your system for malware by running

rkhunter -c


download from here

 # wget
 # tar xvfz lynis-1.1.8.tar.gz
 # ./lynis --check-update
 # ./lynis -c

MD5 sum checks

  • debsums - Verify installed package files against MD5 checksums (Debian systems)
  • md5sum

Generate a checksum for the partition you wish to image, run from shell

# md5sum /dev/hdc2 > /tmp/hdc2.md5

To make the copy of the disk(s), we'll use the dd command. From shell…

# dd if=/dev/hdc of=/tmp/hdc.img

You will need enough space in /tmp to hold a copy of the entire /dev/hdc drive. This means that /tmp shouldn't be a RAM disk and should not be stored on /dev/hdc. Write it to another hard disk !

ids.txt · Last modified: 2009/05/25 00:35 (external edit)
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