How does a proxy sever get past a firewall?

So my school uses a firewall called smoothwall to keep us from going to a various number of websites, so i figured out that using a proxy server, in this case its Tor, would let me get past web panel that pops up. How exactly does this work?

firewalls block incoming traffic, correct?

and proxies only disguise your ip to the web server right?

so in theory smoothwall should block the website no matter what, right?

sorry i'm just confused about this whole topic and because most of you on here seem like pretty smart individuals i figured i'd just ask

thanks in advance for answers :)

Edit:

My school uses a firewall called Smoothwall to keep us from going to a various number of websites, so I figured out that using a proxy server, in this case its Tor, would get past the firewall. How exactly does this work?

Since the proxy only changes your IP how does it get round the filter since the web request would still remain the same.

TheAmazing_OMEGA

Posted 2014-03-06T14:32:08.363

Reputation: 1

When you try to circumvent your school's firewall you should keep in mind that this firewall was put up for a reason. It is very likely that you can get in quite serious trouble when you get caught—and for good reason, too. Just some advice; I cannot answer the rest of question, though. – Vucar Timnärakrul – 2014-03-06T14:41:51.680

Tor does a bit more than just "change your IP." It maintains connections to other Tor nodes, creates circuits, and encrypts your traffic before sending it out. – LawrenceC – 2014-03-06T15:37:54.967

@Vucar thanks i know i was only using it to get to an online textbook because the firewall was going whack and blocking everything, – TheAmazing_OMEGA – 2014-03-06T16:20:02.467

@ultrasawblade yeah sorry i was wrong about "changes your ip" i know how it works now thanks for the info about Tor though :) – TheAmazing_OMEGA – 2014-03-06T16:21:46.710

Answers

The way a web proxy works in this case is that it fetches the site on your behalf.

For instance, let's say that your school blocks Facebook. In simplest terms, this is roughly what happens:

Your firewall blocks Facebook
You go to the proxy - not Facebook.
The proxy requests Facebook's homepage for itself, not you.
The proxy's firewall isn't blocking Facebook.
The proxy displays the content from its own website to you.
Your school firewall sees incoming traffic from "Tor", not Facebook.
The proxy doesn't block it.
You see the site.

Proxies don't just hide your IP, they fetch a site on your behalf and present it as if it was their content. The web servers at Facebook would be getting a request from Tor - not you, this is how the "hiding your IP" portion of proxying comes into play.

Make sense? Also, it's worth noting that if the school goes to the effort of blocking stuff, they probably monitor traffic and will investigate heaps of traffic going to Tor.

Also, lots of schools also block anonymisers and proxies too.

Lastly - you will get in heaps of trouble if caught, so don't do it, but since your question was more of a "how does it work?" instead of a "how can I?" There's your answer.

Fazer87

Posted 2014-03-06T14:32:08.363

Reputation: 11 177

Really glad it helps... Just don't do anything stupid and get yourself in trouble at school.. its not worth it. – Fazer87 – 2014-03-06T14:50:02.680

Some proxies, such as Tor for example, will also encrypt your traffic, which also makes it difficult for content filters to block your traffic. – heavyd – 2014-03-06T14:59:26.297

alright thanks that clarifies a lot! i was actually using Tor to get to an online textbook because the firewall went whack and started blocking everything but a few sites. i actually was wondering about this because i was talking with one of the moms who drives my carpool, and we were trying to figure out if Tor could be blocked long story short we ended up discussing this issue. Also Tor works on a network of relay points that exist all around the world with different iP addresses for each one so it would be pretty difficult to block, No? – TheAmazing_OMEGA – 2014-03-06T15:01:03.537

Depends on the firewall... If the firewall can only block IPs, yes its difficult - if it can block host/domain names (tor.xyz) or wildcards (tor) then its a lot easier. A college I once worked for blocked (youtube) and a couple of other subdomains - a lot easier than hundreds of IPs – Fazer87 – 2014-03-06T15:06:43.547

so i seems that Tor exit nodes can be blocked and there's a list published online hmmm..... i honestly do wonder if the IT guys here will actually block Tor.... – TheAmazing_OMEGA – 2014-03-06T15:42:19.400

Well,m theres only 1 real way to find out - but if the IT guys are monitoring it, i wouldn't recommend it! – Fazer87 – 2014-03-07T09:09:00.727

If you're using Tor to access websites, it also uses Peer-to-peer connexions to get to a website, it's like using a simple proxy server, but in large scale and spread in all over the world. Tor will fetch the website from a computer (like mine for example) that has a non-blocked internet access for you.

Tarek Jellali

Posted 2014-03-06T14:32:08.363

Reputation: 136