I was seeing this question which was concerned with blocking access to the users who do not belong to a particular region. I am sure that blocking is possible but I see there is a workaround to this. I login to the region's proxy from here.I give this URL as the site to visit.Now, I am in the region's proxy and I am able to login to the serveras well.Is there a way to reject such circumvented attempts in the iptables? I see this as a pretty dangerous security concern. 
Reject ssh connections made from proxies
ssh;security;iptables;firewall
This question looks very confused, but I think the confusion is part of the question, so I'll try to provide enough background to clarify things.HTTP and SSH are different protocols. HTTP is spoken by HTTP clients (called web browsers) and HTTP servers (called web servers). SSH is spoken by SSH clients and SSH servers. The HTTP protocol has a notion of proxy, where a network node receives an HTTP requests from a client and forwards it to a server, and forwards the response back from the server to the client. SSH doesn't have proxies in the technical sense; however a machine that allows people who aren't using it physically to use an SSH client on it is acting as a proxy in the general English sense of the term.http://www.freeproxy.ca/ lists HTTP proxies. They aren't useful to make SSH connections.http://www.serfish.com/console/ is a machine that runs an SSH client which is driven from a publicly accessible web interface. If you use a web browser to connect to serfish, and run the SSH client there, then as far as the SSH server is concerned, your connection comes from serfish, full stop. There is no way for the SSH server to know that the SSH client is being driven by someone who isn't physically located in the datacenter where serfish is hosted. Note that it doesn't matter whether you're accessing serfish directly over HTTP or via an HTTP proxy; the SSH server has no way to know anything about that.In general, a server can only know about the last hop used to connect to it. Is this a security concern? Yes, but hardly a dangerous one. Filtering connections by geographical origin cannot be done reliable; any moderately competent system administrator knows that. Geographical origin can give a clue as to whether a connection is suspicious, but it can't be the only factor. There are machines infected by malware and used as relays all over the world.The security of SSH doesn't rely on geographical origin of connections. Filtering by geographical origin is done for only two purposes:For content distribution, to restrict what the non-technical 95% of the audience can do (setting proxies requires digging further than a majority of people are willing to do) and make things a bit more inconvenient for the technical 5% (proxies need to be paid or searched for, and reduce performance).As a hint that a connection to an account comes from an unusual location  but that's usually done at a finer-grained level than a country, which is too broad to provide a very useful hint. Some systems use this to decide whether to require a second authentication factor.The flip side of not being able to track the ultimate origin of an SSH (or any) connection is that some amount of privacy is possible.