Ports?

hey, I have looked through quite a few of the tutorials...but there isn't much (that I could find) on ports. Now I could be looking in the wrong places (most likely)...but anyways, Can someone just give me a bit of info on ports, and what they do? That would be a great help...and also, from my understanding, Hackers can enter your system via ports, how do they do this?? and is there a way to stop them? I have Zone alarm running, and also another nifty little program that tells me if anyone is looking at my ports...so yeah, if some peeps can answer this, or point me in the right direction I would be very greatful :)
Thanks.

I'm sure you found some pretty nice google tutorials on the site, hm, anyway ::


Ports are doors into computers. Hosts are computer names.
(ip number or a name that is translated into the ip automatically)
Different programs open different ports, but they always open the same ports so other computers know which port to connect to. You can get a port list listing all the different ports, but a basic one is:
11 :- Sends info on the computer
21 :- FTP (File transfer program)
23 :- Telnet (Login to the computers command line)
25 :- Smtp (Sends mail)
80 :- Http (Web pages)
There are thousands of different programs using different ports. You can get programs called portscanners which check a computer for all ports up to a certain number, looking for ways in. You can portscan a computer looking for ways-in.

( the link to this info is pretty groovy, so im not mentioning the source, but it's not me )


Some extra links:


List of Ports

If you can convert through a language convertor , here's some german for you : Here

Thanks alot! Am I going the right way about stopping people accessing my comp??
one more thing...I am a little confused about how someone can actually access your comp via the ports...I mean its all well and good that these ports open for certain things, or is there a way to manipulate the ports and allow something else in??

Thanks again, I sorta know whats going on now :D

Of course hades, you're going the right way stopping people to access your computer.
I dont think it can be explicitly mentioned here how you enter ports and manipulate what.
Read the first line of post(#2) in this discussion.
That just about tells ya what to do.

Alrighty, thanks a lot :D

I just thought I would mention a few things. First, invader did a good job listing the main ones that a "normal" Internet user would connect to (although I do not know about 11, invader maybe you could explain that one to me). If you want a more thorough list of ports (port numbers can range from 0 to 65535) go to http://www.iana.org/assignments/port-numbers.

Second, you have to remember that even if you use a personal firewall (ZoneAlarm is an excellent choice), your safety is not guaranteed. You should disable any services that you do not want. For Windows 95 - Me, you should only need to worry about File Sharing (I don't know about XP Home). Windows NT - XP Pro come with additional services (sorry, I cannot tell you how to disable them). Make sure your OS is always updated with the latest security patches. Make sure you have (and use) anti-virus software. It would be possible for a trojan writer to program his/her trojan to bypass ZoneAlarm, so you should also run a port scan on yourself every once in a while. Depending on how paranoid you are, you can follow any of the steps I have recommended. You are definitely on the right track with ZoneAlarm though.

Hey, I gotsta question for you guys. Are ports something different than the Hub Linksys system, because I've got a Cable/DSL router for my RR, but also have a 20 Hub/Port Linksys system that takes 20 different devices with external cable extensions and hooks them up on one network. The funny thing is, all this time i've been thinking that there are only 20 ports, my main question is, where are the other 65515 ports that are supposedly in my computer-if the 20 Hub/Port Linksys system is actually part of the entire 'port network.'

Hi Jag. It sounds to me - although I am not sure - that you could be confusing physical ports on your hub with the "doors" to your computer. A hub is merely a device that is used to connect multiple machines on a network among other things. Basically, every time one of the machines on your network needs to communicate with another, it goes to the hub which broadcasts the message out to every physical port to find the destination. For small home networks, they are very efficient; however, as a network gets bigger, a hub becomes less feasible. At this point, switches may need to be introduced as a more "intelligent" device. How so, they actually learn the MAC address of the connected devices, thus reducing the noisy broadcast traffic. As far as the ports of which we are speaking, they are - as already has been mentioned - doors to your computer. However, they are more software than hardware, so don't think of them as physical hardware connections. Look at it like this: think of your computer as an apartment building with many, many apartments (around 65,000 or so). Now, in order to get mail to the proper place, you need two things - the building number, and the apartment number. Consider the building number your machine's IP address and the apartment number your port number. You need both to deliver information to the right application (telnet, smtp/mail, DNS, ...). The first 1024 ports are considered well known and include the ones mentioned. I hope that helped you a bit. I apologize if I am totally off here, but this is how I interpreted your post.

t2k2

TCP/UDP port 11 is for Systat... In the unix world it was originally going to be used for remote process monitoring, the whole idea fell a bit short.

you can find the RFC at http://www.cis.ohio-state.edu/cgi-bin/rfc/rfc0866.html if you truly crave more information...