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As many web developers can attest to, logging into your server through SSH (Secure Shell) is one of the more common day-to-day tasks (you can even use it as a secure tunnel for your traffic). It only makes sense to automate this process which in turn can save many many keystrokes.

This how-to is written with PuTTY and Windows in mind and requires several other tools that are available from PuTTY’s website. So from their download page, make sure you have these files:

• PuTTY (putty.exe)
• PuTTYgen (puttygen.exe)

Then to automate SSH login, do the following:

1. Run PuTTYgen.
2. Select SSH-2 DSA as the Type of Key to generate.
3. Click generate and move your mouse around to generate randomness.
4. Click “Save Private Key” and save it somewhere on your computer.
5. Copy the entire content inside the box to your clipboard (this is your generated public key).
6. Login to your SSH server.
7. Create the file ~/.ssh/authorized_keys containing the generated public key (from step 3) on a single line.
8. Make this file readable (chmod 755).
9. Then open up PuTTY and navigate to Connection->Data and fill in the auto-login username.
10. Navigate to Connection->SSH->Auth and under Private-key, browse to the file you had saved earlier on your computer.

That’s it! Now you can try logging in to your SSH server and it should login automatically. If it works, make sure you save your session so you don’t have to repeat these steps every time!

Hopefully these steps work for everyone! Let me know if there are any problems.

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Using Wi-fi in public hotspots can be dangerous when packet sniffers are readily available. You’d want to encrypt and protect what you are sending and receiving over the network. Even at home if you don’t want people on the network logging your activity (for whatever reason) you would want to encrypt your traffic. An excellent way to do this is to set up a proxy over an SSH connection. You will need the following to do this (works for any platform):

• PuTTY for your platform (I use v0.59)
• A server that supports SSH (either set up at home or your web host)

That’s it! First set up PuTTY to connect to your SSH server but also set the following Tunnel settings:

• Source Port: 7070 (this number can be pretty much anything)
• Destination: localhost
• Select Dynamic and Auto

Then click Add and it should show up as D7070. Select Open and log-in. Your traffic can now be forwarded once you configure your applications to use the proxy.

In Firefox (2.x), go to Tools->Options->Advanced->Network->Settings and set the following proxy configuration:

• Manual proxy config
• SOCKS Host: localhost
• Port: 7070
• SOCKSv5 (or v4, doesn’t matter)

Then hit OK and you’re done. To make sure the proxy is working, you can go to a site that will display your IP address or location. You can also encrypt your BitTorrent traffic or your MSN connection by changing connection/proxy settings to point to localhost port 7070 using either SOCKS v4 or v5.

An easy way to switch proxy settings in Firefox is to install the Switchproxy add-on — change proxy settings with just a click. Enjoy your secure browser session!

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What is BFD (Brute Force Detection)?
BFD is a modular shell script for parsing applicable logs and checking for authentication failures. There is not much complexity or detail to BFD yet and likewise it is very straight-forward in its installation, configuration and usage. The reason behind BFD is very simple; the fact there is little to no authentication and brute force auditing programs in the linux community that work in conjunction with a firewall or real-time facility to place bans. BFD is available at: http://www.rfxnetworks.com/bfd.php

This guide will show you how to install and configure BFD to protect your system from brute force hack attempts.

Requirements:
- You MUST have APF Firewall Installed before installing BFD - it works with APF and requires some APF files to operate.
- Root SSH access to your server

Updated: April 13, 2005

Lets begin!
Login to your server through SSH and su to the root user.

1. cd /root/downloads or another temporary folder where you store your files.

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

3. tar -xvzf bfd-current.tar.gz

4. cd bfd-0.7

5. Run the install file: ./install.sh
You will receive a message saying it has been installed

.: BFD installed
Install path: /usr/local/bfd
Config path: /usr/local/bfd/conf.bfd
Executable path: /usr/local/sbin/bfd

6. Lets edit the configuration file: pico /usr/local/bfd/conf.bfd

7. Enable brute force hack attempt alerts:
Find: ALERT_USR=”0″ CHANGE TO: ALERT_USR=”1″

Find: EMAIL_USR=”root” CHANGE TO: EMAIL_USR=”your@yourdomain.com”

Save the changes: Ctrl+X then Y

8. Prevent locking yourself out!
pico -w /usr/local/bfd/ignore.hosts and add your own trusted IPs
Eg: 192.168.1.1

Save the changes: Ctrl+X then Y

BFD uses APF’ cli insert feature
and as such will override any allow_hosts.rules entries users have in-place.
So be sure to add your trusted ip addresses to the ignore file to prevent
locking yourself out.

9. Run the program!
/usr/local/sbin/bfd -s

10. Customize your applicatoins brute force configuration
Check out the rules directory in your /usr/local/bfd

Here you’ll find all kinds of pre-made rules for popular services such as Apache, and ProFTPD w00t!
If you have any clue about shell scripting you can customize them or create new rules for enhanced brute force detection and prevent attacks.

Thanks to RFX Networks for creating another great script for the community, Brute Force Detection is excellent!

Cheers

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What is APF (Advanced Policy Firewall)? APF Firewall
APF is a policy based iptables firewall system designed for ease of use and configuration. It employs a subset of features to satisfy the veteran Linux user and the novice alike. Packaged in tar.gz format and RPM formats, make APF ideal for deployment in many server environments based on Linux. APF is developed and maintained by R-fx Networks: http://www.rfxnetworks.com/apf.php

This guide will show you how to install and configure APF firewall, one of the better known Linux firewalls available.10

Limit SSH connections to one IP with APF in this advanced tutorial

Requirements:
- Root SSH access to your server

Lets begin!
Login to your server through SSH and su to the root user.

1. cd /root/downloads or another temporary folder where you store your files.

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

3. tar -xvzf apf-current.tar.gz

4. cd apf-0.9.5-1/ or whatever the latest version is.

5. Run the install file: ./install.sh
You will receive a message saying it has been installed

Installing APF 0.9.5-1: Completed.

Installation Details:
Install path: /etc/apf/
Config path: /etc/apf/conf.apf
Executable path: /usr/local/sbin/apf
AntiDos install path: /etc/apf/ad/
AntiDos config path: /etc/apf/ad/conf.antidos
DShield Client Parser: /etc/apf/extras/dshield/

Other Details:
Listening TCP ports: 1,21,22,25,53,80,110,111,143,443,465,993,995,2082,2083,2086,2087,2095,2096,3306
Listening UDP ports: 53,55880
Note: These ports are not auto-configured; they are simply presented for information purposes. You must manually configure all port options.

6. Lets configure the firewall: pico /etc/apf/conf.apf
We will go over the general configuration to get your firewall running. This isn’t a complete detailed guide of every feature the firewall has. Look through the README and the configuration for an explanation of each feature.

We like to use DShield.org’s “block” list of top networks that have exhibited
suspicious activity.
FIND: USE_DS=”0″
CHANGE TO: USE_DS=”1″

7. Configuring Firewall Ports:

Cpanel Servers
We like to use the following on our Cpanel Servers

Common ingress (inbound) ports
# Common ingress (inbound) TCP ports -3000_3500 = passive port range for Pure FTPD
IG_TCP_CPORTS=”21,22,25,53,80,110,143,443,2082,2083, 2086,2087, 2095, 2096,3000_3500″
#
# Common ingress (inbound) UDP ports
IG_UDP_CPORTS=”53″

Common egress (outbound) ports
# Egress filtering [0 = Disabled / 1 = Enabled]
EGF=”1″

# Common egress (outbound) TCP ports
EG_TCP_CPORTS=”21,25,80,443,43,2089″
#
# Common egress (outbound) UDP ports
EG_UDP_CPORTS=”20,21,53″

Ensim Servers
We have found the following can be used on Ensim Servers - although we have not tried these ourselves as I don’t run Ensim boxes.

Common ingress (inbound) ports
# Common ingress (inbound) TCP ports
IG_TCP_CPORTS=”21,22,25,53,80,110,143,443,19638″
#
# Common ingress (inbound) UDP ports
IG_UDP_CPORTS=”53″

Common egress (outbound) ports
# Egress filtering [0 = Disabled / 1 = Enabled]
EGF=”1″

# Common egress (outbound) TCP ports
EG_TCP_CPORTS=”21,25,80,443,43″
#
# Common egress (outbound) UDP ports
EG_UDP_CPORTS=”20,21,53″

Save the changes: Ctrl+X then Y

8. Starting the firewall
/usr/local/sbin/apf -s

Other commands:
usage ./apf [OPTION]
-s|–start ……………………. load firewall policies
-r|–restart ………………….. flush & load firewall
-f|–flush|–stop ……………… flush firewall
-l|–list …………………….. list chain rules
-st|–status ………………….. firewall status
-a HOST CMT|–allow HOST COMMENT … add host (IP/FQDN) to allow_hosts.rules and
immediately load new rule into firewall
-d HOST CMT|–deny HOST COMMENT …. add host (IP/FQDN) to deny_hosts.rules and
immediately load new rule into firewall

9. After everything is fine, change the DEV option
Stop the firewall from automatically clearing itself every 5 minutes from cron.
We recommend changing this back to “0″ after you’ve had a chance to ensure everything is working well and tested the server out.

pico /etc/apf/conf.apf

FIND: DEVM=”1″
CHANGE TO: DEVM=”0″

10. Configure AntiDOS for APF
Relatively new to APF is the new AntiDOS feature which can be found in: /etc/apf/ad
The log file will be located at /var/log/apfados_log so you might want to make note of it and watch it!

pico /etc/apf/ad/conf.antidos

There are various things you might want to fiddle with but I’ll get the ones that will alert you by email.

# [E-Mail Alerts]
Under this heading we have the following:

# Organization name to display on outgoing alert emails
CONAME=”Your Company”
Enter your company information name or server name..

# Send out user defined attack alerts [0=off,1=on]
USR_ALERT=”0″
Change this to 1 to get email alerts

# User for alerts to be mailed to
USR=”your@email.com”
Enter your email address to receive the alerts

Save your changes! Ctrl+X then press Y
Restart the firewall: /usr/local/sbin/apf -r

11. Checking the APF Log

Will show any changes to allow and deny hosts among other things.
tail -f /var/log/apf_log

Example output:
Aug 23 01:25:55 ocean apf(31448): (insert) deny all to/from 185.14.157.123
Aug 23 01:39:43 ocean apf(32172): (insert) allow all to/from 185.14.157.123

12. New - Make APF Start automatically at boot time
To autostart apf on reboot, run this:

chkconfig –level 2345 apf on

To remove it from autostart, run this:

chkconfig –del apf

13. Denying IPs with APF Firewall (Blocking)
Now that you have your shiny new firewall you probably want to block a host right, of course you do! With this new version APF now supports comments as well. There are a few ways you can block an IP, I’ll show you 2 of the easier methods.

A) /etc/apf/apf -d IPHERE COMMENTHERENOSPACES
> The -d flag means DENY the IP address
> IPHERE is the IP address you wish to block
> COMMENTSHERENOSPACES is obvious, add comments to why the IP is being blocked
These rules are loaded right away into the firewall, so they’re instantly active.
Example:

./apf -d 185.14.157.123 TESTING

pico /etc/apf/deny_hosts.rules

Shows the following:

# added 185.14.157.123 on 08/23/05 01:25:55
# TESTING
185.14.157.123

B) pico /etc/apf/deny_hosts.rules

You can then just add a new line and enter the IP you wish to block. Before this becomes active though you’ll need to reload the APF ruleset.

/etc/apf/apf -r

14. Allowing IPs with APF Firewall (Unblocking)

I know I know, you added an IP now you need it removed right away! You need to manually remove IPs that are blocked from deny_hosts.rules.
A)
pico /etc/apf/deny_hosts.rules

Find where the IP is listed and remove the line that has the IP.
After this is done save the file and reload apf to make the new changes active.

/etc/apf/apf -r

B) If the IP isn’t already listed in deny_hosts.rules and you wish to allow it, this method adds the entry to allow_hosts.rules

/etc/apf/apf -a IPHERE COMMENTHERENOSPACES
> The -a flag means ALLOW the IP address
> IPHERE is the IP address you wish to allow
> COMMENTSHERENOSPACES is obvious, add comments to why the IP is being removed These rules are loaded right away into the firewall, so they’re instantly active.
Example:

./apf -a 185.14.157.123 UNBLOCKING

pico /etc/apf/allow_hosts.rules

# added 185.14.157.123 on 08/23/05 01:39:43
# UNBLOCKING
185.14.157.123

Thanks to R-fx networks for developing and maintaining APF Firewall.

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Want to be notified instantly when someone logs into your server as root? No problem, check out this nice tutorial on email notification for root logins. Keeping track of who logs into your server and when is very important, especially when you’re dealing with the super user account. We recommend that you use an email address not hosted on the server your sending the alert from.

So lets get started!

1. Login to your server and su to root, I know the irony!

2. cd /root

3. pico .bashrc

4. Scroll to the end of the file then add the following:
echo ‘ALERT - Root Shell Access (YourserverName) on:’ `date` `who` | mail -s “Alert: Root Access from `who | cut -d”(” -f2 | cut -d”)” -f1`” you@yourdomain.com

Replace YourServerName with the handle for your actual server
Replace you@yourdomain.com with your actual email address

5. Crtl + X then Y

Now logout of SSH, close the connection and log back in! You should receive an email address of the root login alert a few minutes afterwards.

Note: This is a great tool for servers that have multiple admins or if you give someone SSH access for whatever reason, although you should give out the root password to as few people as humanly possible and be sure to change it often.

This will not magically alert you when a hacker runs the latest kernel exploit on your server and logs into SSH because they will create their own SSH/telnet connection. You should keep your system up to date, install a firewall and follow the latest security releases.

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Chkrootkit is a powerful tool to scan your Linux server for trojans. We’ll show you how to install it, scan your server and setup a daily automated scanning job that emails you the report.

Installing CHKROOTKIT

SSH as admin to your server. DO NOT use telnet, it should be disabled anyways.

#Change to root
su -

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

# Check the MD5 SUM of the download for security:
ftp://ftp.pangeia.com.br/pub/seg/pac/chkrootkit.md5

md5sum 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‘…

Important Note: If you see ‘Checking `bindshell’… INFECTED (PORTS: 465)’ read on.
I’m running PortSentry/klaxon. What’s wrong with the bindshell test?
If you’re running PortSentry/klaxon or another program that binds itself to unused ports probably chkrootkit will give you a false positive on the bindshell test (ports 114/tcp, 465/tcp, 511/tcp, 1008/tcp, 1524/tcp, 1999/tcp, 3879/tcp, 4369/tcp, 5665/tcp, 10008/tcp, 12321/tcp, 23132/tcp, 27374/tcp, 29364/tcp, 31336/tcp, 31337/tcp, 45454/tcp, 47017/tcp, 47889/tcp, 60001/tcp).

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

Daily Automated System Scan that emails you a report

While in SSH run the following:
pico /etc/cron.daily/chkrootkit.sh

Insert the following to the new file:
#!/bin/bash
cd /yourinstallpath/chkrootkit-0.42b/
./chkrootkit | mail -s “Daily chkrootkit from Servername” admin@youremail.com

Important:
1. Replace ‘yourinstallpath’ with the actual path to where you unpacked Chkrootkit.
2. Change ‘Servername’ to the server your running so you know where it’s coming from.
3. Change ‘admin@youremail.com’ to your actual email address where the script will mail you.

Now save the file in SSH:
Ctrl+X then type Y

Change the file permissions so we can run it
chmod 755 /etc/cron.daily/chkrootkit.sh

Now if you like you can run a test report manually in SSH to see how it looks.
cd /etc/cron.daily/

./chkrootkit.sh

You’ll now receive a nice email with the report! This will now happen everyday so you don’t have to run it manually.

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APF firewall can deny ALL connections for ssh and allow only a single or select few of IPs to connect to your server. We’ll guide you through DENY ALL with APF firewall.

PROBLEM:
You want to deny all IPs to connect to shell/ssh on you server but only allow a select one or few to connect with APF firewall.

APF SOLUTION:
1) Login to your server as the root user.

2) cd /etc/apf

3) Use vi or nano to edit the /etc/apf/allow_hosts.rules file
EG: vi /etc/apf/allow_hosts.rules

4) Scroll down until after their last comment with the ##

Add the following in:

tcp:in:d=22:s=YOURHOMEIPHERE
out:d=22:d=YOURHOMEIPHERE

The d=22 part is the port, so you can repeat for other services as well to limit connections if you like.

Save the changes.

5) Edit the /etc/apf/deny_hosts.rules file
EG: vi /etc/apf/deny_hosts.rules

Scroll down until the last default comment ## then below it add the following:

tcp:in:d=22:s=0/0
out:d=22:d=0/0

Save the changes.

6) Restart APF firewall
apf -r

Your server is now only allowing connections to the SSH service from one IP using APF. To add more than one IP repeat the steps in 4) adding a new tcp and out line for each IP.

Cheers

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