How to Bypass Most Firewall Restrictions and Access the Internet Privately

aka The Surf At Work Page
pwc21@yahoo.com  http://www.buzzsurf.com

Created: 10/25/2002   Last Updated: 8/3/2004
 
Contents

Introduction
More and more employers and universities are becoming aware of the amount of time their employees or students are spending using the Internet for personal reasons. Obviously employers want to discourage this behavior and may implement a number of different ways to do so. These can include;
  • Restricting people from installing programs on their workstation. This usually won't stop someone from accessing Web sites, but it may keep people from playing games or using instant messaging software.
  • Using a firewall or proxy server to restrict access to web sites or other Internet protocols. All your Internet communication passes through your network's firewall, so it's a great place to monitor and restrict access. How complex or restrictive it is largely depends how tech savvy your IT department is.
  • Using a network monitoring system to "spy" on Internet access. This is a form of firewall monitoring, where your employer can intercept and read/save anything flowing through their firewall. Your IT department may call this an Intrusion Detection System, which is primarily used to monitor for attempted hacker attacks or viruses.
  • Installing programs on workstations that monitor Internet access. This is probably the toughest thing to get around because there are so many different vendors that offer this type of software. In addition, there is software that simply records every keystroke you press. In most cases, there's no way around this other than disabling the software.
This guide discusses a way an employee or student can securely access the Internet while at work or school, and also get around common firewall restrictions that prevent you from using most networked programs. My definition of "securely" means that there should be no mean by which your employer can know which web sites you have visited or are currently visiting, and can not view or decipher the content of those sites (without actually standing over your shoulder.)

Keep in mind that the method I discuss here will protected you from NETWORK monitoring, not actual computer or keystroke monitoring. So if your IT department has some security software installed on your PC, you probably shouldn't even be looking at this page.

In addition to protecting you from network monitoring, this method can be used to get around a number of other security protections that may be in place;
  • Your employer or school allows access to most of the Internet but blocks certain websites that they consider non work related. Using this method you can access them.
  • Your employer or school blocks you from chatting at work using MIRC or ICQ or similar instant messaging programs. Follow my instructions and you will be able to get around the firewall and chat at work.
  • You want to access your employer or school's Intranet from home. Setup the shunnel in the reverse order as I describe, with the proxy and SSH server on your work computer, and the SSH client at home. You'll be able to access Intranet websites from home just like you were sitting at your work computer.
This version of the guide demonstrates how to encrypt your network traffic using an SSH tunnel to an HTTP proxy server. There could be other means to achieve this objective, which I may discuss in future versions. Using this method will actually allow you to do more than just surf the web privately. You can secure any program that can use an HTTP proxy. This includes most instant messaging software like ICQ, AIM, Yahoo! IM, MSN, mIRC and others.

A couple people have asked me about this method as it relates to a VPN (Virtual Private Network). A VPN will typically let you access your work network from home, which this method can do also (to a degree). The difference is that with a VPN, your entire computer is configured like it's on your work network. So no matter what application you use, it will have a work IP address and respond just like you are at work.

The method on this page just uses a proxy, so for browsing websites, it works. Anything else you want to do on your work network probably won't work. Things like telnet, mapping network drives, PCAnywhere, to name a few. You could consider this a psuedo VPN or virtual VPN. My advice however is, if you have the choice of using a VPN, always use it.

Overview
The objective is to encrypt your network traffic so it can not be read as it passes through your employer or school's network. To do this, we will;
  • Run an HTTP proxy server on your computer at home.
  • Run an SSH server on your computer at home.
  • Use an SSH client on your computer at work to create a secure tunnel between your home and work computers.
  • Configure Internet Explorer to use the SSH client as a proxy.
After this is all setup, the process for browsing a website will be as follows. Internet Explorer at work connects to the SSH client running on your computer at work. The SSH client connects to the SSH server running on your computer at home. The SSH server at home connects to the proxy server running on your computer at home. The proxy server talks to the website and returns the web page to the SSH server. The SSH server returns the web page to the SSH client. The SSH client return the web page to Internet Explorer.

In essence, you are tricking Internet Explorer into thinking you have a proxy server running on your local machine, when in fact the proxy is running on your computer at home. Since all communication over your work network takes place through SSH, it can not be read. The SSH traffic CAN be seen, but it will look like a garbled mess of letters and numbers. Other than being a little slower than usual, you shouldn't notice any difference when surfing the web when using the secure method.

Some people that are familiar with SSH and may be asking, "How can Internet Explorer talk to SSH?". Well, SSH has a great little function called Connection Forwarding. You setup SSH to accept TCP connections on a port and forward them to a port on another computer. SSH takes ALL the network traffic on that port, wraps it in a secure package, and forwards it somewhere else. I refer to this as a "shunnel"; a secure tunnel.


Audience
This guide is written for a moderately skilled computer user. You MUST know how to install programs on your computer, how to navigate file systems, and how to edit configuration files. A knowledge of "how the Internet works", like TCP, sockets, ports, HTTP, and other network protocols would be extremely helpful.

Prerequisites
To use this method, you need the following;
  • A decent computer at home that you can leave connected to the Internet all day while you're at work.
  • A fast Internet connection at home; usually cable or DSL. (Technically, this can work with a dialup modem connection, but it may cause problems and it's really slow.)
  • Microsoft Windows NT, 2000, or XP installed on your computer at home and any flavor of Windows on your computer at work. You may be able to get this to work with 95, 98, or ME, but I can't say for sure. You definitely can get this to work with Linux or Unix. I don't know about Macintosh.
When won't this work?
Please notice the title of this page starts "How To Bypass Most Firewall Restrictions... I say most because the method I describe here will not work for everyone, even if you meet the pre-requisites above. If any of the following are true for you, you probably can't use this method successfully;
  • You can not access any external Internet websites; only internal websites or none at all.
  • You can access a few specific Internet websites, but no others at all.
  • You are already configured to access the Internet through a proxy server.
    To check this on your work computer, open Internet Explorer, click on Tools, then Internet Options. Click Connections, then click LAN Settings. There should be a check box on that page next to the sentence "Use a proxy server for your LAN." If this box is checked, then you are already using a proxy.
If any of the 3 lines above apply to you, your network administrator is working hard because they are using a "pessimistic" blocking strategy. In other words, they have decided to block everything, and probably only allow specific access. The problem with that strategy however, is that it requires much more work and maintenance than using an "optimistic" strategy, in which they allow access to everything and block only certain "things".

The method I describe on this page will not work with a pessimistic blocking strategy because it depends on being able to access your home computer from work. 9 times of 10, if you can't get to www.amazon.com, you won't be able to your home computer either. If for some reason you CAN access your home computer, then great.. proceed If not, you may want to talk to your network administrator. Ask him if they would punch a hole in the firewall so you can SSH to your computer at home. Or come up with some excuse to get access to 1 port on your home computer, then run the SSH server on that port.

Or... maybe you ARE the network administrator and are just curious about how this works. :)

Addresses
Before we start installing and configuring software, you need to find out the following things;
  • Your home IP Address
  • Your work/school external IP Address
The easiest way to get your IP Addresses is to go to www.whatismyip.com at home and at work. Write down the numbers.

Software
We're going to be using three major pieces of software; an HTTP proxy server, an SSH Server, and an SSH Client.

Any HTTP proxy server will probably work, but I'm going discuss how to setup Apache as our proxy. Apache is the most widely used HTTP server on the Internet. It includes mod_proxy, an add in module that will allow it to function as a proxy server. It's free and secure and not too hard to setup.

Download Apache for Windows from http://httpd.apache.org/download.cgi. The version I am using for this document is 2.0.47. I recommend downloading the latest version and using the .msi installer.

There are a few flavors of SSH Server's out there, but we're going to be using OpenSSH because it's free. The website for OpenSSH is http://www.openssh.com. But wait! OpenSSH doesn't run on Windows unfortunately... But there is a site that converted OpenSSH to run on Windows, which is what we want! http://sshwindows.sourceforge.net/.

Download OpenSSH for Windows from http://sourceforge.net/project/showfiles.php?group_id=103886&package_id=111688. The version I wrote this document using was 3.7.1p1-1. The latest version should work for you.

For the SSH Client I recommend using Putty. Putty is a small single executable SSH client with the ability to setup a tunnel. It's possible to use OpenSSH as your client as well as your server, but Putty is much easier to setup and use. Download putty.exe from http://www.chiark.greenend.org.uk/~sgtatham/putty/download.html.

Install Apache
On your home computer, run the Apache install program you downloaded. Choose Typical Install, and install as a service on port 80 (we'll change later). The install should ask for the following;
  • Network Domain; Enter 127.0.0.1
  • Server Domain; Enter 127.0.0.1
  • Administrator Email Address; Enter your email address
Apache should install into C:\Program Files\Apache Group\Apache2. If you choose to install into a different location, that fine, but be aware I will use the above path in this document. It should also create a program group in your Start menu called "Apache HTTP Server 2.0.47" or something similar.

Note; Apache 2 includes an annoying little feature called the "Apache Monitor". It's a service that plants itself in your system tray and tells you when Apache is running. If you don't mind it, then leave it. Otherwise go into your start menu, find the "Startup" group, and delete the entry for it. After that it won't run unless you start it up yourself.

Configure Apache
Note for all Windows users! Many of the configuration files we will be editing are in native Unix format. This means that Windows Notepad will not read them correctly. Use Wordpad instead. If you open a Unix text file in Notepad and all the words run together on the same line, and sentences are separated by little black boxes, that means it's in Unix format. Open it in Wordpad and it will look normal.

We want to configure Apache to listen on port 8080, and we want to enable the proxy server so the local host (and ONLY the local host) can connect and use it.

From the Start Menu run "Edit the Apache httpd.conf Configuration File" under the Apache group/Configure Apache Server.

Remove the # sign in front of the following 4 lines;

LoadModule proxy_module modules/mod_proxy.so
LoadModule proxy_connect_module modules/mod_proxy_connect.so
LoadModule proxy_http_module modules/mod_proxy_http.so
LoadModule proxy_ftp_module modules/mod_proxy_ftp.so

Then, change the line

Listen 80

to

Listen 8080

Then, find the section that looks like this:

#
# Controls who can get stuff from this server.
#
Order allow,deny
Allow from all

Change it to look like this:

#
# Controls who can get stuff from this server.
#
Order deny,allow
Deny from all
Allow from 127.0.0.1

Finally, find the line "Section 3: Virtual Hosts".  Right above that line, add the following text:

<IfModule mod_proxy.c>
 
ProxyRequests On
 
<Proxy *>
Order deny,allow
Deny from all
Allow from 127.0.0.1
</Proxy>
 
# If you plan to use mIRC, uncomment the following line
#AllowCONNECT 6666 6667 6668
 
</IfModule>

Big fat extremely important note!

There's currently a major problem on the Internet with "Open Proxies." An Open Proxy is a proxy server that allows anyone to connect to it and send requests. Open proxies are a problem because spammers can use them to relay bulk mail anonymously. What's worse, it looks like the spam is coming from the proxy, which would be YOU!

Please use the sample code above. It will only allow proxy requests from the local machine, which makes it secure. Since the SSH server will be running on the local machine, that's all you need to allow.

After making these changes, save httpd.conf. From the same program group in the Start Menu, run Test Configuration. If you made all the changes correctly, a black box will flash and then disappear. If you made any mistakes, a black box will appear and tell you where you screwed up. Go back and fix it.

Install SSH
The OpenSSH installer comes in a zip file. Unzip the file, then run setup371-xxxxx.exe. The name of the file will depend on the last time they built it, and when you download it. Choose to install both the Client and the Server. It will ask you to install into C:\Program Files\OpenSSH. If you choose to install into a different location, that fine, but be aware I will use the above path in this document.

Configure Windows
OpenSSH for Windows uses Windows' user database for login authentication. That mean you must have a User name and Password setup to login to your home computer. If you don't, you have 2 choices. 1, set a password on your Windows account, or 2, create a new local account that you will use to login from SSH. I know a lot of people out there don't use logins or passwords on their home computer, but if you're using NT, 2000, or XP, the functionality is there, even if you don't use it.

There are many different flavors of Windows, with different methods of creating a local user. There's no way I can cover all of them, but here are a few examples;

To create a new account on your home machine (Windows XP):
  • Start Menu, open Control Panel, then User Accounts.
  • Click Advanced tab, then the Advanced button.
  • Highlight Users, then click Actions, then New User.
  • Enter a User name, and a Password twice. I recommend you use a User name and Password that is different than anything you have ever used at work. Obviously, your employer probably knows your password, so there's no security if you use the same password at home.
  • Deselect User must change password at next logon.
  • Check Password never expires.
  • Click Create.
  • Close the Windows, close Control Panel.
You should now have a new local Windows user on your home machine. Remember the Login name and password for later.

Configure SSH
We want to configure your SSH server to allow access using User name and Passwords, and to listen on port 443 instead of port 22.

Why port 443 instead of port 22? In most cases your employer will block almost all outgoing network ports except for port 80 and port 443, which are the 2 ports that web servers run on. I used to tell people to run SSH on port 80 because that's the standard web server port, but now I recommend you run it on 443. Port 443 is used for encrypted websites, which is what your shunnel traffic will look like as it passes through the firewall. If you have trouble on port 443, try it on port 80 instead. If neither work, you're probably out of luck.

Open Windows Explorer, navigate to C:\Program Files\OpenSSH\etc. Open the file sshd_config using Wordpad. (That's sshd_config not ssh_config!)

Change the line

#Port 22

to

Port 443

Save the file.

Now open a command prompt. Change to C:\Program Files\OpenSSH\bin. We are going to create a user and group database from your Windows user database. Type the following;

mkgroup -l > ..\etc\group

Then

mkpasswd -l > ..\etc\passwd

These 2 commands will create group and password files at C:\Program File\OpenSSH\etc

Start/Stoping Apache and SSH
On your home computer, open a command prompt. To start your servers, type the following:

net start opensshd
net start apache2

To stop your servers type the following:

net stop opensshd
net stop apache2

To make it easy, you can create a .bat file that will execute the 2 commands. If you make a shortcut to the .bat file in your Windows startup group, then when you turn on your home computer in the morning, the servers will startup automatically, and be ready for you when you get to work.

If you have a wired or wireless router at home (Linksys, D-Link, Netgear, etc)
Some routers call it port forwarding and others call it virtual servers, but the setup is very similar no matter what brand you use. You will need to configure your router to route port 443 to the computer where you're running the SSH server. I not going to go into details, but there is usually a browser based interface directly to the router, which will have a page to setup virtual servers. Configure it to forward port 443 to your SSH computer, port 443.

Setup Putty at Work/School
Copy putty.exe to somewhere on your hard drive at work. c:\ will do fine, or anywhere else you want. Your desktop is convenient but kind of obvious. If you don't have permissions to write files to your hard drive, just copy putty.exe and shunnel.bat to a floppy disk or burn them onto a CD. Take the disk to work and run Putty from the appropriate drive.

Open Notepad and copy the following into it, change the bold parts where necessary;

"putty -L 80:127.0.0.1:8080 -ssh homeIP -port 443"
  • homeIP should be the IP address of your home machine that you wrote down in the Addresses section above.
Save the file as shunnel.bat in the same directory that you saved putty.exe.

Create your tunnel
At work, simply double click shunnel.bat to initiate the shunnel. A Putty window will popup asking for a login name and password. Type the user name and password you created above on the Windows account. If it works, you will be presented with a DOS prompt waiting for a command. This is actually a command prompt to your HOME machine. You can use it if you want, but as long as this command prompt is open, your tunnel is alive. To close the tunnel, type exit or close the window.

For Advanced Users
If you are very familiar with SSH and know what you are doing, you can set this up so you don't have to enter a password each time you create the shunnel. You have to install OpenSSH as your SSH client and then setup key based authentication by creating a public and private key on your work computer. Install the public key on the SSH server on your home computer. Create shunnel.bat using this command "start "shunnel" /B "C:\Program Files\OpenSSH\bin\ssh" -l userID -c blowfish -p 443 -C -N -2 -L 80:127.0.0.1:8080 homeIP" Thanks to Robert W. for this suggestion. I may go into more detail on how do set this up in the future.

Configure Internet Explorer
Now we'll configure Internet Explorer at work to use a proxy server.

First, go to http://www.whatismyip.com. Write down the number. This is your work IP address without the private connection enabled.

In Internet Explorer, open the Tools menu, then click Internet Options. Click the Connections tab, then click LAN Settings. Check "Use a proxy server" and enter the following:

Address: 127.0.0.1
Port: 80

Click OK. Close Internet Explorer and restart it.

First, go to http://www.whatismyip.com again. If everything worked correctly, the page should have changed to show your HOME IP address, NOT your work IP address. If it shows your home IP Address, congratulation, your surfing the web securely and privately from work.

Configuring other applications to use the private connection
Most applications that access the Internet can be configure to use the shunnel. For it to work, they have to support an HTTP proxy connection. Instant messaging programs like AIM, ICQ, Yahoo IM, and mIRC all support this.

Setup is different for all application, but the settings will be the same. You want to configure the application to use an HTTP proxy server, Host should be 127.0.0.1, and Port should be 80.

Protect yourself from someone looking over your shoulder
Here's a great application that fits in perfectly with the theme of this page. It's called Ghostzilla; http://www.ghostzilla.com/. The idea is that you want to surf the web, but have it look like you are doing normal work to people walking by your computer. Ghostzilla is a browser that hides itself in your normal work applications, like Excel, or Word, or Visual Studio... anything. With a swish of the mouse, Ghostzilla pops up and you can surf the web. If you see someone coming, simply move the mouse away, and it disappears, leaving no trace. Plus, you can easily configure it to use the shunnel as described here, for total privacy!


Copyright © 2002-2004 BuzzSurf.com - All rights reserved.
Please do not repost or retransmit the content of this page.
You are welcome and encourged to link to the page.

http://www.buzzsurf.com/surfatwork

BY VIEWING THIS PAGE, YOU EXPRESSLY AGREE THAT ALL RISKS ASSOCIATED WITH THE METHOD DESCRIBED ABOVE IS ASSUMED SOLELY BY YOU. THE AUTHOR SHALL NOT BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF USE OF THE METHOD. THE METHOD IS MADE AVAILABLE BY THE AUTHOR "AS IS" AND "WITH ALL FAULTS". THE AUTHOR MAKES NO REPRESENTATIONS OR WARRANTIES AS TO THE TRUTH, ACCURACY OR COMPLETENESS OF ANY INFORMATION ON THIS PAGE.


Notes:

11/21/2002 - The page is starting to pickup in popularity. I'm interested to know if anyone else has been successfully in getting it to work. Drop me an email. Thanks.

11/21/2002 - Please email me if anyone notices errors or security holes!

01/17/2003 - Changed to use Putty as an SSH Client instead of OpenSSH. Thanks to James.Q.L for this suggestion.

01/22/2003 - Added Ghostzilla blurb.

03/05/2003 - Added Amazon Honor System links to ask for donations. Check it out!

03/19/2003 - Changed theme a bit to highlight ability to bypass a firewall. Based on google searches, getting around a firewall is actually more popular than protecting privacy.

05/22/2003 - Changed recommended SSH port from 80 to 443. Should work just as well on 443 and set off less alarms because traffic on port 443 is encrypted anyway.

06/02/2003 - Chopped page up into "concept" and "description" pages. Now asking for donations to access the description page.

09/11/2003 - Added link to Amazon Wish List

09/13/2003 - Updated Apache instructions to version 2.0.47

09/25/2003 - Updated OpenSSh instructions to version 3.7.1. A security flaw was found in version 3.4 that I was previously using! All users whould upgrade to 3.7.1 or higher.

01/14/2004 - Page resurrected after being down for a few months... Server died, sorry! On temporary hosting until new server is ready.

01/22/2004 - Hosting on rebuilt server.

08/03/2004 - Updated some broken links and changed a few minor wording issues.


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