Solved

How does a firewall work exactly?

Posted on 2004-04-11
3
422 Views
Last Modified: 2013-11-16
Firewall blocks a connection to a remote computer on a certain port(let's say that I'm trying to connect to that remote comp on port 545 or 1531 for example), but would firewall block connection if that remote comp is trying to connect on me (if I don't have a firewall) on port: 545 or 1531?

Can anyone explain or send me a link of some great firewall tutorials. First I would like to know basics about firewalls and then all complicated stuff and all of tiny details of their function. How to avoid firewalls?
0
Comment
Question by:vbr666
3 Comments
 
LVL 20

Expert Comment

by:What90
ID: 10800930
I've always thought this was good:
http://computer.howstuffworks.com/firewall.htm
0
 
LVL 10

Accepted Solution

by:
LRI41 earned 113 total points
ID: 10803339
 Firewall Tutorials

Internet Firewall Tutorial
A White Paper
July 2002
 
What a firewall does
http://www.rpanetwork.co.uk/wp/fw.rhtm


How to Configure Windows XP to Work with IRC
or
15 Easy Steps to a Fully Functional Firewall and IRC Client Under Windows XP

http://newircusers.com/xp.html




--------------------------------------------------------------------------------
 
July 2002• Vol.13 Issue 7  

Security
Understanding Firewall Alerts

http://www.smartcomputing.com/editorial/article.asp?guid=gxz5usb0&article=articles/2002/s1307/52s07web/52s07web.asp 


0
 
LVL 8

Expert Comment

by:RLGSC
ID: 10804503
VBR666,

Firewalls look at messages going between one side and another. Messages are only allowed to pass through if they are deemed not a danger, and within policy. In all but the most trivial cases, the direction does count (a request inbound to say, the FTP port, is not the same as an outbound request to somebody else's FTP port).

The degree of checking varies depending upon the firewall (and the rules that are configured for it).

Depending upon the rules and the firewall, the checking can be quite extensive. In the simplest cases, the checking is done based upon the direction of the request, and the port number. More complex checking can include source and destination addresses, time of day, and examintation (And regulation) of the data stream itself.

The Computer Security Handbook (4th Edition) has a good chapter on firewalls (as well as many other good chapters on security issues).

- Bob (aka RLGSC)
0

Featured Post

Free Tool: Subnet Calculator

The subnet calculator helps you design networks by taking an IP address and network mask and returning information such as network, broadcast address, and host range.

One of a set of tools we're offering as a way of saying thank you for being a part of the community.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Wikipedia defines 'Script Kiddies' in this informal way: "In hacker culture, a script kiddie, occasionally script bunny, skiddie, script kitty, script-running juvenile (SRJ), or similar, is a derogatory term used to describe those who use scripts or…
Do you have a windows based Checkpoint SmartCenter for centralized Checkpoint management?  Have you ever backed up the firewall policy residing on the SmartCenter?  If you have then you know the hassles of connecting to the server, doing an upgrade_…
Although Jacob Bernoulli (1654-1705) has been credited as the creator of "Binomial Distribution Table", Gottfried Leibniz (1646-1716) did his dissertation on the subject in 1666; Leibniz you may recall is the co-inventor of "Calculus" and beat Isaac…
The Email Laundry PDF encryption service allows companies to send confidential encrypted  emails to anybody. The PDF document can also contain attachments that are embedded in the encrypted PDF. The password is randomly generated by The Email Laundr…

837 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question