Computer Ports

The number one way a computer is exposed for nefarious uses online is by
exploiting open ports on that system.

Ports are names or "handles" given to various network connections your com-
puter uses to communicate with other computers. For example, your connection
to the Internet is through a port protocol called TCP/IP (Transmission Control
Protocol /Internet Protocol) using well-known ports such as HTTP or "port 80".
While it sounds complicated, the way all this works is actually fairly simple.

A program (called a "daemon" in Unix or a "service" in Windows) "listens" or
watches a specific port. So, for instance, a web server daemon will watch port
80 for queries from outside the server. When a query comes in, the daemon
immediately responds by accepting the query and sending the requested
information.

On a home computer, many of these ports are open by default, many for good
reason, but many more for no good reason. Trojan horse programs (software
that pretends to be one thing, but is actually another), AdWare (software that
runs using online advertising), SpyWare (software that "spies" on your activity
in order to target advertising to you, or for other reasons), and other questionable
or downright devious programs will listen at unusual ports to send or receive
information. Information that you may not want transmitted.

There are several ways to check these ports and ensure that they are OK. The
best and easiest is to use a software firewall such as ZoneAlarm:
(http://www.qksrv.net/click-983614-9925654) to monitor your incoming and
outgoing data and alert you to anything suspicious. I highly recommend this
route for most users.

If you are a little more technical and/or more adventurous, you can open a
command window (MS-DOS window in Windows) and type the command
"netstat" "an" at the prompt (no quotes) and see a list of currently open ports
and the IP addresses associated with them.

Often overlooked, open ports are the easiest and most common way for a hacker, virus, or worm to take advantage of your computer or data. Learning about the open ports on your machine and how to guard them is important.