Proxy Server and Packet Filtering

 Proxy Server

            It’s a server that acts as a bridge for requests from the clients seeking resources from other servers.  A client connects to the proxy server, requesting some services, such as a file, connection, webpage or other resources available from the different server.

Advantages of Proxy Server

1. Provides anonymity on the Internet, since there is no direct link between you and the server.
2. It can be used to block undesired sites.
3. Can be used to log the Internet usage of the users in a specified network.
4. Can also provide some features which are generally found in Firewalls & Intrusion Prevention Systems such as scanning the transmitted content for Malwares before delivery.
5. They are also used to scan outgoing traffic to prevent data leakage.

Note: Proxy Server that does not change any request (Incoming/Outgoing) is usually considered as a Gateway.

Types of Proxy

1. Caching Proxy Server
2. Web Proxy Server
3. Content Filtering Server
4. Anonymizing Proxy Server
5. Hostile Proxy
6. Transparent Proxy Server
7. Reverse Proxy

Caching Proxy Server

It keeps a cache of frequently opened/accessed WebPages, images and other media. The advantage of having cache is that reduces the bandwidth consumption of the network, since Fresh Request is not made for the same content.

A disadvantage is that, it may not work well for websites, images and other media which is very frequently updated.

Web Proxy Server

It’s a server which only serves the HTTP Traffic. It can be used to block URLs that contains blacklisted words or websites. Mostly found in Corporate Networks.

Content Filtering Servers

It provides more control over the Internet that is passing through the Proxy Server. It’s usually used in combination with web proxy servers.
It also supports user authentication to control internet access and it also helps in monitoring the type of traffic generated by individual users which may be employees of a company or students in a university.

Anonymous Proxy Server

It’s used to hide the user’s identity while using the Internet. They are deployed as open proxy and are difficult to track. Mainly used by hackers.

Hostile Proxy:

It’s a server which eavesdrops upon the data flow between its clients and the Internet.

Data can be easily interprets passing through it which can be passwords or important files.

Transparent Proxy Server

Is a proxy that does not modify the request or response beyond what is required for proxy authentication and identification.

A Non-Transparent Proxy is a proxy that modifies the request or response in order to provide some added services to the user agent.

Intercepting Proxy Server

Also known as “Hidden Proxy” . It associates itself with the Network’s Gateway or Router. All the Traffic originating in the network has to pass through the Proxy Server, even if the user has no specific configuration for using the proxy. The user won’t even be aware that the Proxy Server exists on the Gateway of the Network.

Reverse Proxy Server

All types of proxy servers we have studied till now are forward proxy servers i.e. they forward clients request to the server, acting as a mediator in between.

It requests server request to the client.

Types of Web Proxy Servers

Transparent Proxy

It’s a proxy which reveals the IP address of the Proxy being used as well as the IP address of the client who is suing the Proxy Server.

Anonymous Proxy

It’s a proxy which hides the IP address of the client who is hiding behind it, however using certain techniques, the server can figure out if the connection is routed through a Proxy or if it is Direct.

Risks: Data sent through the proxy server can be easily seen as that data is mostly sent in an unencrypted form.

Elite Proxy

It’s a proxy which hide the user in such a way that it makes it very difficult for a Server to trace back whether the request is coming from the proxy server or if it’s coming through the original user. Elite proxy servers are usually paid and available by paying money.

Socket Chain Proxy

Is a program that allows working with any Internet Service through a chain of SOCKs or HTTP proxies to hide the IP address.

Tor Proxy (The Onion Routing Project)

It is a system intended to enable online anonymity, composed of client software and a network of servers which can mask information about user’s location and other factors which might identify them.

Squid Proxy Server

1. It’s a proxy server which was created in Linux based systems. Now works with Windows too.
2. It is used as a proxy server for monitoring outgoing traffic and to enforce an organization’s rules & policies.
3. It is used to prevent data leakage. Its other uses are to speed up the surfing experience of the users by caching the web, DNS and other computer lookups.

Bypass Proxy Server & Firewall

Http Tunneling is a process by which we can bypass the application based firewalls and proxy servers.

What is Packet Filtering?

Packet Filtering is a process of passing data packets through the network interface based on source & destination addresses, ports, protocols, keywords or URLs. It is normally used in combination with the Firewall. Today latest firewalls are being made with the capability of packet filtering pre-installed.

Difference –Proxy Server & Firewalls

Firewalls works on Packet Filtering, it can apply rules on packets. If we disable the firewall, then anybody can access anything from the Internet and the network will be unrestricted.

Whereas, Proxy Server works on application level & applies ACLs for URLs and keywords to decide whether the packets will be forwarded or denied. But in case of Proxy Server, if it is disabled, the Traffic going through it would cease and all requests would become unreachable.