Unblockus.com: how does it work?

Nils hit the nail on the head. To use Unblock Us, you have to change your DNS servers to point to theirs.

When you visit a webpage, your computer accesses the DNS server to determine the IP address of the web-server hosting the site.

Normally, you get the IP address from the DNS server and fetch the page from the server at that address. When you do that, your system includes your IP address in the network packet containing the fetch request. The web-server sees that, and it can refuse to serve the page based on that (or any other factor).

When you use Unblock Us’ DNS servers, instead of returning the IP address of the destination site, it returns the address of one of its own proxy servers (which are located in the US). Now, when you fetch a page from the target website, instead of requesting it from the actual web-server of the site, you are requesting it from Unblock Us’ server (in the US). Then their server forwards the request onto the target site which then sees the IP address of the proxy instead of yours. Because the proxy is in the US, the target site returns the data which gets forward to your system. You can see this system in action by pinging one of the supported before and after activating their DNS servers.

They only support a small set of sites. For other sites that don’t require geo-location or sites that they just don’t support (yet?), they return the IP address of the real server.

This means that to implement your own system, you will still need a with an IP address in the US.

You may be interested in Tunlr, which is a service just like Unblock Us, except free. Their explanation of how it works is better Unblock Us’:

How does it work?

Tunlr does not provide a virtual private network (VPN). Tunlr is a DNS (domain name system) unblocking service. We’re using sophisticated technologies (a.k.a. the Tunlr Secret Sauce ©) to re-adress certain data envelopes, tricking the receiver into thinking the envelope originated from within the U.S. For these data envelopes, Tunlr is transparently creating a network tunnel from your location to our U.S.-based servers. Any data that’s not directly related to the video or music content providers which Tunlr supports is not only left untouched, it’s also not even routed through Tunlr. In order to use Tunlr, you will have to change the DNS address.

Looks like the service works via their custom DNS servers.  I imagine that for 99% of host names they will just return the real IP address of the server, but for the sites that Unblock-Us works on they will return the IP address of a custom proxy server, which will then tunnel your connection through a US-based connection.  This way you don’t get the performance hit of a VPN, since it doesn’t tunnel anything that doesn’t have to be tunneled.

There are many VPN services that do that for you. Here's how it works:

• Your connection is identified by an IP address, which is where web pages or streming videos are sent after you request them with your browser. Likewise, any service on the internet has an IP address, which is where your browser requests pages.

• The IP is typically, but not necessarily, assigned to you temporarilry by your internet provider. Large ISPs and servers usually have pre-bought IPs which never change.

• There are companies, most notably MaxMind, who keep track of where each IP is geographically located. This is known as geolocation.

• A service may use geolocation to determine whether to serve you or block you or send you to a localized version of its pages.

Now, here's the trick:

• A VPN service (a virtual private network) is a service where you can channel all your communications to the outside world through a remote server. For example, if the company you work for offers you VPN, all your computer's activity could be channeled through a server inside the company network and thus your computer would appear as to be part of the company's intranet.

• There are other commercial VPN services that offer no-question-asked, full broadband IPs to appear as if you were browsing from the location identified by their server's IP address. They usually have a list of servers and locations to choose from.

• Commercial VPNs have generally a latency cost. Since all your communication go through a foreign server, data has to travel a lot more to get to your computer. This is usually perceived as slower bandwidth. For this reasons, some VPN companies now offer "virtual country" IP addresses, where the server is located near you, but the geolocated country corresponding to its IP is one of your choice.

I tend to travel a lot and use one of these services to access Netflix, BBC etc when I'm abroad. It works perfectly, with the added advantages of giving me an encrypted connection to the internet (typically one's connection is exposed in open WiFIs like hotels and airports) and of being virtually anonymous, because my real IP is hidden.

That said, though, Unblockus seems to be different from a VPN. I was misled by their page title when I answered above ("Unblock-Us - smarter faster VPN").

The way their system works is that they take over your DNS configuration. What are DNS? They are services that translate a site name, like "netflix.com" into an IP, as explained above, like "69.53.236.17". By taking over this service, when you type "netflix.com" in your browers, the IP address returned will not be Netflix's but their own. They can then proceed to "proxy" your connection just like a VPN provider would do. In other words they will ask for the page or video on your behalf, and then send it, or stream it, back to you.

The concept is very similar to a VPN with simpler configuration, but it will have some (many) caveats.

• it won't work with services specified by IP
• it will throw stern warnings if the site is encrypted. or make the connection less secure (I hope not!)
• it generally will lower your security because all the data will transit through their servers unencrypted (not so with a real VPN provider), although the communication to their servers might be encrypted.
• their service might be selective: they might not proxy some servers like Google.

Perhaps using a VPN connection would work in your case, you can setup a router that supports VPN and tunnel all your home network traffic and it would appear as if you are located in the US, it will be transparent to all your local PCs and SmartTV etc.

• Services like unblockus.com or unotelly work mainly for things like Netflix/Hulu etc. but the VPN service would change all your traffic also in your computers, you will get Google US etc.

I believe UnblockUs uses a combination of proxy servers / mirrors of the services they support and reroute traffic to these servers by having clients go through their DNS servers.