“I
know internet”
Browser(Friend)
: Ok. Let me apply my trick and get back to you with the resource you
are looking for.
Browser
To Name Server: Can you translate the server name to IP Address(DNS
Does This!) ??I need the IP ?
Name
Server: Ok Translated and Take the IP. “123.123.234.55”
[Browser
Connected to the IP]
Browser
to Server(Via IP): I have sent you a “GET” request . Did you see
that ? Actually I need
“naughty-css-injection-how-bad-it-is.html
” file.
Server:
Take The file.
Summary:
- Person typed the URL
- Browser get the URL and Broke it to 3 parts and read the server name.
- Communicated with the DNS server to get the IP address.
- Connected to the IP using a Port no.
- Sent a GET Request
- Got the file as a response.
Firewalls:
Say we have a company
having 500 people. How should we implement Firewall ??
“Out
of the 500 computers inside this company, only one of them is
permitted to receive public FTP traffic. Allow FTP connections only
to that one computer and prevent them on all others. ”
In
Simple words Firewall stop connecting to all 500 systems.
Firewalls
use one or more of three methods to control traffic flowing in and
out of the network:
- Packet filtering - Packets (small chunks of data) are analyzed against a set of filters. Packets that make it through the filters are sent to the requesting system and all others are discarded.
- Proxy service - Information from the Internet is retrieved by the firewall and then sent to the requesting system and vice versa.
- Stateful inspection
- A newer method that doesn't examine the contents of each packet
but instead compares certain key parts of the packet to a database
of trusted information. Information traveling from inside the
firewall to the outside is monitored for specific defining
characteristics, then incoming information is compared to these
characteristics. If the comparison yields a reasonable match, the
information is allowed through. Otherwise it is discarded.
For
example, if a certain IP address outside the company is reading too
many files from a server, the firewall can block all traffic to or
from that IP address.
Firewall vs Proxy
Servers
Firewalls can block
ports and programs that try to gain unauthorized access to your
computer, while proxy servers basically hide your internal network
from the Internet. It works as a firewall in the sense that it blocks
your network from being exposed to the Internet by redirecting Web
requests when necessary.
Continue.....
