Ports can be physical (hardware) or virtual (software) ...
Did you know that if you do
not specifically tell your computer's Operating System to use a port
(really an opening in the NIC's software structure) it will leave those
closed for any use? They are opened by a specific service.
Services are defined by IANA here if you need a full explanation. At this time IANA lists over 49151
of them that have been named and standardized. See (RFC 3692 for details about the assignments and criteria)
Note: In the computer world a RFC is a document that puts forth a theory for comments, Request For Comments, after the theory is thoroughly discussed it may or may not become a standard. If it becomes a standard the RFC number is quoted in documentation about the standard, listing all the persons involved in the comments and so forth.
To enable a service or disable a service on Windows, Unix, or Linux operating systems you would edit the "services" file located in the etc folder/directory.
Note: There are two types of them defined for a computer:
- Service port- a service uses to gain access through the
network or dial up connection,
- Physical port - they extend the physical dimensions of the
computer such as the USB, Keyboard, or Video connectors.
For Windows this folder/directory path is Windows/System32/Drivers/Etc and the file called "services" no extension.
When a Windows service is installed either by the installation process or you add hardware/software to your computer and it requires a service the process will write the service name and number in the service file and for Windows in the Service key for the registry.
Unknown fact: "If you disable or remove a service from the Windows
Registry it does not turn off the service
When the Operating System starts it reads the registry and the services file
and enables any of them listed in both.
Thus disabling a service through the Service Manager will not disable
it, only by editing the services file will the it be disabled.
Now why would you care if it was disabled when the service was disabled through the Service Manager?
Because an open one not being used by the service that enabled it is an open security hole that a virus/thief could potentially exploit to gain access to your computer then your data!
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And there are a lot of Services that are opened by the Operating System when the install process has completed.
I counted over 200 on my Windows XP installation alone. (I haven't checked Vista or Windows 7 service file as of yet).
Now do I need all those that are open? No, but the question is which ones to remove from the services file to insure they are not open?
That will take some research, first each one is not named by the service that would need it, as an example your email needs two:
SMTP and POP (or POP3) to communicate with your email provider, turning these off if you use an email client such as Outlook, Eudora, or The Bat would effectively stop communication between the client program and your email service provider.
However if you use a web based email such as GMail, Live, or one of the other services then turning (removing the statement) from the services file will stop those two from functioning thus enhancing your security.
If you use a software "Firewall" solution such as Windows Firewall service
Self Computer Repair Unleashed! 2nd Edition Manual Chapter 6 for configuring this service) you could do the same thing by "blocking"
it from being accessed, this may be a better and easier solution for some people that don't want to change a file that they know nothing about.
Bottom line on services: If you don't know what it does don't remove it from
the services file. Do your research on which ones you don't know what they are for or you may be reloading the Operating System on your computer.
By turning off or blocking unused ones you will enhance the security of your computer ... :)