how do computer programs connect to the internet? [closed]

Question

I've got a question that came to me from my worry about spyware, I've recently discovers that spam e-mails have been sent from my g-mail to my contacts, even though I changed my password, I am worried I may be keylogged,

What I want to know is if I do have a keylog, it must send my information over the internet in some way,

so first thing I want to ask is how to programs connect to the internet? do they do so through the browser or establish there own connection?

second thing, if they do establish their own connection and I block them with firewall, can programs make a connection through the browser or other common programs and send my information that way? if so, how is this done and can I block this?

Overall I'd like to read up on that, haven't found any info online about how computer programs establish internet connections,

Answer 1

how computer programs establish internet connections

You should read about sockets.

how to programs connect to the internet? do they do so through the browser or establish there own connection?

They establish their own connection to a specific IP and port. The browser is a specific HTTP client application to connect to HTTP servers.

If you believe there is a malicious program running in your PC possibly making connections to a remote host, sending personal information, you can do a netstat to see all connections and verify that are from legit programs. If you see connections from "unknown" programs then it is likely that your PC has been infected. You can also use a packet sniffer to see what information is send from your PC.

Answer 2

Here is the wiki all about spyware http://en.wikipedia.org/wiki/Spyware