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Chkrootkit

Thu, 15 Dec 2005 21:43:05 +0000

Installing CHKROOTKIT

(Version 0.42b Sep 20 2003)

SSH as admin to your server. DO NOT use telnet

#Change to root
su -

#Type the following
wget ftp://ftp.pangeia.com.br/pub/seg/pac/chkrootkit.tar.gz

#Unpack the tarball using the command
tar xvzf chkrootkit.tar.gz

#Change to the directory it created
cd chkrootkit*

#Compile by typing
make sense

#To use chkrootkit, just type the command
./chkrootkit

#Everything it outputs should be 'not found' or 'not infected'...

#Now,
cd ..
#Then remove the .gz file
rm chkrootkit.tar.gz

Credits: http://www.cheetaweb.com/

APF Firewall 0.9.4-7

Thu, 15 Dec 2005 21:32:07 +0000

Just thought I'd update the howto's for APF.

Type ifconfig

Find out if it�s using eth0 or eth1.

Usually its eth0 but if its not, change it in conf.apf or you�ll be completely blocking the server from access

wget http://www.rfxnetworks.com/downloads/apf-current.tar.gz

tar -xvzf apf-current.tar.gz
cd apf*
./install.sh
pico -w /etc/apf/conf.apf

RESV_DNS="1"

All SYSCTL options should be set to 1 EXCEPT for
SYSCTL_OVERFLOW="0"
SYSCTL_SYNCOOKIES="0"

USE_DS="1"
USE_AD="1"

FOR PLESK:

IG_TCP_CPORTS="20,21,22,25,53,80,110,143,443,465,993,995,8443"
IG_UDP_CPORTS="37,53,873"

EGF="1"
EG_TCP_CPORTS="20,21,22,25,53,37,43,80,113,443,465,873"
EG_UDP_CPORTS="53,873"

For CPANEL:

IG_TCP_CPORTS="20,21,22,25,53,80,110,143,443,993,995,2082,2083,20 86,2087,2095,2096"
IG_UDP_CPORTS="37,53,873"

EGF="1"
EG_TCP_CPORTS="20,21,22,25,37,53,43,80,113,443,465,873,2087,2089"
EG_UDP_CPORTS="53,873"

apf �s to start firewall.

If you are not kicked out of SSH and you can type commands after it loads, that means it�s installed correctly.

pico -w /etc/apf/ad/conf.antidos

LP_KLOG="1"

USR_ALERT="1"
USER = �root�
ARIN_ALERT="1"

pico -w /etc/apf/conf.apf

change DEVM to 0

apf -r

Antidos via APF Firewall

Thu, 15 Dec 2005 21:30:45 +0000

Antidos is a really nice feature of the APF firewall, but it's not automatically turned on when you install and run APF.

First you probably want to make sure APF is running nicely for a few days and you have your own IP listed in the "allow_hosts.rules" file so you can't lock yourself out. You also want to understand how to access the EV1 remote console (from your EV1 account manager), just in case you do lock yourself out.

And to be even more safe, lets set DEVEL_MODE to "1" (on) and we need to setup USE_AD to enable the use of antidos, so find and edit these:

pico -w /etc/apf/conf.apf

DEVEL_MODE="1"

USE_AD="1"

apf -r

Now APF will quit in 5 minutes. Don't forget to put DEVEL_MODE back when everything is OK!

Your server will not be firewalled after 5 minutes! If you are under attack right now this might not be such a good thing to disable.

If you installed APF with the normal installer most of the settings for antidos should be OK. We only need to change a few things, find and change these:

pico -w /etc/apf/ad/conf.antidos

LP_KLOG="1"
IPT_BL="1"

USR_ALERT="1"
USER = �root�
ARIN_ALERT="1"

You can test run it manually (it's just a shell script):

/etc/apf/ad/antidos -a

It doesn't say anything if it liked the config file and your system, and if you ran it for the first time, you will find it created a blank log file at:

/var/log/apfados_log

You need to have antidos set to run via cron. If you have "crontab -e" all set up you can use that to set it up. Some panels let you edit the root cron job file from the panel.

This is a critical setup point, if not done, antidos will simply not operate.

Here's an example line, I added this to my root crontab:

*/2 * * * * /etc/apf/ad/antidos -a > /dev/null 2>&1

This will run antidos every two minutes. The author of antidos doesn't recommend running it once a minute as it may cause a bottleneck for itself and the CPU. Likewise running it beyond a period of once every 5 minutes is not recommended either, for obvious reasons.

You can check to see if it's being run with something like this:

tail -30 /var/log/cron

Now restart apf again:

apf -r

Try to access a few of your sites and if you are not locked out and happy with everything you can set DEVEL_MODE to "0" (off) :

pico -w /etc/apf/conf.apf

DEVEL_MODE="0"

apf -r

At this point it would be nice to test to see if it actually works, I leave that up to you to figure out how or maybe someone else can post some ideas. I would be very careful, you don't want to DOS the wrong server.

If for some reason you find out it's locking the wrong people out and want to turn it off, take this line out of root cron:

*/2 * * * * /etc/apf/ad/antidos -a > /dev/null 2>&1

And blank out this file:

/etc/apf/ad/ad.rules

You can look in the log file to see what went wrong:

/etc/apf/ad/apfados_log

And don't forget to restart apf:

apf -r

For more info on the settings, see the doc files at:
http://rfxnetworks.com/apf.php

Banning over-aggressive web crawlers

Thu, 15 Dec 2005 21:03:11 +0000

Not all web crawlers obey robots.txt like they should

One in particular was getting on my nerves, the Inktomi Slurp crawler. Essentially, it would go to my site (http://rpg-works.net) and load ALL my clients sites in quick succession, bogging down my server to the point of becoming unresponsive.

So, for your benefit, here's my current ban list (I put this in rc.local)

# Ban Slurpy (Inktomi/Yahoo) NetBlock
/sbin/iptables -A INPUT -s 66.196.64.0/18 -j DROP
# Ban nameprotect.com
/sbin/iptables -A INPUT -s 12.175.0.32/28 -j DROP
# AskJeeves.Com
/sbin/iptables -A INPUT -s 65.214.36.0/22 -j DROP
# Alexa
/sbin/iptables -A INPUT -s 209.237.238.0/24 -j DROP
# Turnitin.com Bot
/sbin/iptables -A INPUT -s 64.140.49.66 -j DROP
# Cyveillance.com (RIAA enforcement)
/sbin/iptables -A INPUT -s 63.148.99.224/27 -j DROP

Others here, such as nameprotect.com are "intellectual property" crawlers that basically check your site for compliance. Even though they use your bandwidth and resources, you get nothing in return (such as listing on a search engine), they're just looking for someone to sue on behalf of one of their clients.

If you're having problems with your server randomly becoming unresponsive, this is worth a shot.

How did I get these IPs?

Check your access logs for "robots.txt", most bots at least attempt to look at the file. The enter those IPs into http://arin.net
for information on who they belong to, as well as the netblock you can ban if the bot is an extreme nuisance.

Mount /tmp with noexec

Thu, 15 Dec 2005 20:20:01 +0000

What we are doing it creating a file that we will use to mount at /tmp.

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

cd /dev

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

Create 100MB file for our /tmp partition. If you need more space, make count size larger.

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

dd if=/dev/zero of=tmpMnt bs=1024 count=100000

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

Make an extended filesystem for our tmpMnt file

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

mke2fs /dev/tmpMnt

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

Backup your /tmp dir- I had mysql.sock file that I needed to recreate the symbolic link for. Other programs may use it to store cache files or whatever.

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

cd /

cp -R /tmp /tmp_backup

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

Mount the new /tmp filesystem with noexec

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

mount -o loop,noexec,nosuid,rw /dev/tmpMnt /tmp

chmod 0777 /tmp

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

Copy everything back to new /tmp and remove backup

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

cp -R /tmp_backup/* /tmp/

rm -rf /tmp_backup

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

Now we need to add this to fstab so it mounts automatically on reboots.

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

pico -w /etc/fstab

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

You should see something like this:

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

/dev/hda3 / ext3 defaults,usrquota 1 1
/dev/hda1 /boot ext3 defaults 1 2
none /dev/pts devpts gid=5,mode=620 0 0
none /proc proc defaults 0 0
none /dev/shm tmpfs defaults 0 0
/dev/hda2 swap swap defaults 0 0

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

At the bottom add

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

/dev/tmpMnt /tmp ext2 loop,noexec,nosuid,rw 0 0

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

(Each space is a tab)

Ctrl + X and Y

Your done- /tmp is now mounted as noexec. You can sleep a little bit safer tonight. I created a hello world c++ and compiled it then moved it to /tmp. Upon trying to run it (even chmod +x'ed), it gives the following error:

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

bash: ./a.out: Permission denied

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

HOW-TO: Secure cPanel

Wed, 30 Nov 2005 21:43:35 +0000

First and foremost I want to say that this is not going to make your server 100% cracker proof, there is always a possibility that somebody will find a way in. I have listed a lot of things you can do to protect your server and that will help you secure it. While securing your server you have to find a median between what is secure and what restricts your clients or websites. You can easily make your server 100% secure from remote attacks by unplugging the ethernet cable, but chances are you will not get much good with it. This is not a complete guide and I will update it when I find time or it needs it. Overall it is a very good start and it is probably more then most servers have.

If you have any problems with the guide please post them and I will try and help/update the guide. I have not included everything you can do but it is a very good start. If you need somebody to secure server please feel free to private message or email me.

All commands meant to be run in ssh will begin with "#"

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

First step is to updated your software. Make sure up2date says you are fully updated:
#up2date -u

Now update the kernel. Below I have posted the directions for a server using lilo as the bootloader. I will add in directions for grub later as I do not run grub on any of my servers. If you are using grub please skip this section and upgrade the kernel at another time.

#cd /var/spool/up2date

If you have a dual processor server:

#up2date --download --force kernel-smp
#rpm -ivh kernel-smp-2.4.21-15.0.4.EL.i686.rpm
#lilo -v -v
#lilo -R 2.4.21-15.0.4.1
#shutdown -r now

If you have a single processor server:
#up2date --download --force kernel
#rpm -ivh kernel-2.4.21-15.0.4.EL.i686.rpm
#lilo -v -v
#lilo -R 2.4.21-15.0.4.1E
#shutdown -r now

When you run lilo -v -v make sure that no errors appear, if so you probably need to look at the lilo.conf for the problem.

The lilo -R command will make it reboot only once to the new kernel. If for some reason just put in a reboot TT and it will automatically boot to the old kernel. If it comes back up fine then you can edit the /etc/lilo.conf and set "default=" the new kernel label.

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

A firewall should be the first thing installed.. I recommend advanced protection firewall (APF) by rfxnetworks. APF will block unused outgoing and incoming ports. It can also be configured to use information from some block lists.
http://rfxnetworks.net/apf.php
#cd /usr/src
#wget http://rfxnetworks.net/downloads/apf-current.tar.gz
#tar -zxf apf-current.tar.gz
#cd apf-0.*
#./install.sh

Now edit config file
#pico -w /etc/apf/conf.apf

Change the following:
USE_DS="1"
USE_AD="1"

Scroll down to this section:

# Common ingress (inbound) TCP ports IG_TCP_CPORTS="20,21,22,25,26,53,80,110,143,443,465,993,995,2082, 2083,2086,2087,2095,2096"
# Common ingress (inbound) UDP ports
IG_UDP_CPORTS="21,53,465,873"

# Common ICMP (inbound) types
# 'internals/icmp.types' for type definition; 'all' is wildcard for any
IG_ICMP_TYPES="3,5,11,0,30,8"

Scroll down a bit then find this section:

EGF="1"
# Common egress (outbound) TCP ports EG_TCP_CPORTS="21,22,25,26,27,37,43,53,80,110,113,443,465,873,208 9"
# Common egress (outbound) UDP ports
EG_UDP_CPORTS="20,21,53,123,465,873"

Save the file and start apf via.
apf -s
If everything still works then edit the config file and turn dev mode off.
DEVM="0"

Now restart APF
#apf -r

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

The following scripts are fairly easy to use and install, I might add documentation later but for now I will not.

Along with installing APF I would suggest installing brute force monitor (BFD) also by rfxnetworks. BFD will monitor your ssh and ftp services and automatically ban users that try to brute force a password. If you install BFD make sure you can get a separate ip to ssh into your server incase it blocks you for some reason! You can add your ip to the allow list via "apf -a IP" if you have a static ip.
http://rfxnetworks.net/bfd.php

Yet another very handy tool by rfxnetworks is socket monitor (PMON). This tool will alert you whenever a new port is opened on the server. This is very helpful in detecting any users running weird processes or attempting to run backdoors. When any program that it does not recognized is started it will email you with the information.
http://rfxnetworks.net/pmon.php

Another tool I would suggest, but that is not really part of securing your server, is system integrity monitor (SIM) which is also by rfxnetworks. SIM will automatically detect when a service is down and restarts it.
http://rfxnetworks.net/sim.php

I always recommend to turn off compilers. Most rootkits come precompiled but not all of them do. It will also prevent shell users from trying to compile any irc related programs. To turn the compilers on switch the off to on.
/scripts/compilers off

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mod_security

First we will download and unzip mod_security. This guide compiles for apache1.3.x which is what cPanel currently uses.
#wget http://www.modsecurity.org/download...ty-1.8.4.tar.gz
#tar zxf mod_security-1.8.4.tar.gz
#cd mod_security-1.8.4/apache1

Next compile mod_security at a module:
#/etc/httpd//bin/apxs -cia mod_security.c

Make a backup of your httpd.conf before touching anything so you have something to go back to if it does not work.
#cp /etc/httpd/conf/httpd.conf /etc/httpd/conf/httpd.conf-mod_sec

Now edit the httpd.conf
pico -w /etc/httpd/conf/httpd.conf

Scroll down below the following line:
AddModule mod_security.c
The rules listed in the text file below can just be pasted in. They are a collection of rules, many of them taken from snort, that block most of the common attacks while still letting normal requests by.
http://eth0.us/faq/modsec.txt

Create the error log file:
#touch /var/log/httpd/audit_log

Restart apache
#service httpd restart

If sites start to have problems look at error log.
/var/log/httpd/audit_log

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

The /tmp partition is one the common places for script kiddies and crackers alike to place trojans or scripts. Because of that you should have the /tmp partition mounted noexec. First we need to check if your /tmp is secure.
#df -h |grep tmp

If that displays nothing then go below to create a tmp partition. If you do have a tmp partition you need to see if it mounted with noexec.
#cat /etc/fstab |grep tmp

If there is a line that includes /tmp and noexec then it is already mounted as non-executable. You will also want to check if /var/tmp is linked to /tmp.
ls -alh /var/ |grep tmp

If it shows something to the effect of "tmp -> /tmp/" then you are ok. If not go ahead an remove the old /var/tmp and replace it with a sym link to /tmp.
#rm -rf /var/tmp/
#ln -s /tmp/ /var/

If you do not have any /tmp partition you will need to follow the directions below to create and mount a partition.

Create a 190Mb partition
#cd /dev/; dd if=/dev/zero of=tmpMnt bs=1024 count=200000

Format the partion
#mke2fs /dev/tmpMnt

Make a backup of the old data
#cp -Rp /tmp /tmp_backup

Mount the temp filesystem
#mount -o loop,noexec,nosuid,rw /dev/tmpMnt /tmp

Set the permissions
#chmod 0777 /tmp

Copy the old files back
#cp -Rp /tmp_backup/* /tmp/

Once you do that go ahead and start mysql and make sure it works ok. If it does you can add this line to the bottom of the /etc/fstab to automatically have it mounted:
/dev/tmpMnt /tmp ext2 loop,noexec,nosuid,rw 0 0

Next delete the old /var/tmp and create a link to /tmp
#rm -rf /var/tmp/
#ln -s /tmp/ /var/

If everything still works fine you can go ahead and delete the /tmp_backup directory.
#rm -rf /tmp_backup

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

Many php exploit scritps use common *nix tools to download rootkits or backdoors. By simply chmod'ing the files so that no none-wheel or root user can use them we can eliminate many possible problems. The downside to doing this is that shell users will be inconvenienced by not being able to use the the commands below. Mod_security really removes the need to chmod this, but it is an added layer of protection.

#chmod 750 /usr/bin/rcp
#chmod 750 /usr/bin/wget
#chmod 750 /usr/bin/lynx
#chmod 750 /usr/bin/links
#chmod 750 /usr/bin/scp

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

Now we will install rkhunter so we will atleast know if the server has been cracked.

Download and unzip rkhunter
#cd /usr/local/src/
#wget http://downloads.rootkit.nl/rkhunter-1.1.4.tar.gz
#tar -zxf rkhunter-1.1.4.tar.gz
#cd rkhunter

Install it
#./install.sh

Now create a cronjob so it will email you with notifications to the root mailbox:
#crontab -e

At the bottom add the following line
16 0 * * * /usr/local/bin/rkhunter -c --nocolors --cronjob --report-mode --createlogfile --skip-keypress --quiet

Press control x to save

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Credits: John W - Security and general linux how-to's