What is a port?
What means closing or opening the ports?

If we imagine that the Internet is like a lawn sprinkler through which passes a large volume of data ports holes would be like a water sprinkler. Internet runs a data flow (water), in that great stream of mixed data travels all services (such as our e-mail, our chat messenger, or whatever we're going down, internet is the great flow and services travel in that stream.

When we connect to our internet provider assigns us a number of ip, this number is unique on the Internet for the duration of our connection among all computers connected to internet in the world, our number is unique. And it's something like 198.123.434.234, that is, four numbers, grouped into three digits.

When we have a router working, it is responsible for filtering each service and refer to your software. For example if you open your email program while we're down some Internet router is responsible for filtering email on port 110 and what we're going down the port 21.

Simile of Internet data stream like a water sprinkler

When we open any program that requires Internet information (like email with port 110) the router opens a port and may enter and exit the port. The problem with this system is that if at that time there is a computer hacker who is crawling on the internet and by chance find our ip number, he will start tracking our open ports.

If at that moment we have opened programs that are allowing the input / output data, the hacker has evidence that behind that IP number is that it was testing a computer with an open software, either email, emule, internet explorer etc.

That's where the firewall does not allow the entry of hackers and is usually installed on the router, firewalls, routers, usually do not allow incoming connections. This is also a problem because there is spyware that, once installed on the machine without the knowledge of the user opens a port, sends a signal to someone who says ... "I'm in this computer and I have opened this port so you can access.

I have written in another article on free software to detect spyware. This article I wanted to spend more security in our router. For this I recommend the service Shields Up!.

Shields Up!!, is a service of Gibson Research that tests the most common ports, you can test them here

Once on this page can do a test of the most common ports or all ports, the page will track your computer and show us if our firewall is working properly.

Shields Up!! window with all options

I recommend doing the test first and then the common port of all ports. If your firewall is working correctly is to give that all ports are "Stealth", meaning that no evidence exists that port on your machine.

Port 21 (that corresponds to FTP) stealth

If it detects open ports, you should close these router ports and/or install a good firewall like Zone Alarm for Windows in your computer, which has a free basic version can be downloaded from here.