As part of your online security you need to have a software firewall. I recommended a couple in an earlier post about Internet Security. First, what exactly is a firewall? Firewalls provide protection against outside attackers by shielding your computer or network from malicious or unnecessary Internet traffic. In a nutshell, a firewall examines the traffic/data coming into and going out of a computer, and then makes a decision to permit or deny this traffic, based on pre-set rules or rules that users have set.
If you’ve been using a software firewall, even one that’s built into your antivirus program, you’ve probably noticed that at times it pops up and asks to allow or deny a program that wants to do something at that time. If you see an access request from the firewall when you first run a program that you know is okay, it’s probably safe to grant access. However, if you get an unexpected access request — one that pops up when you didn’t just start a program — then it’s safer to deny access.
To see if your computer is an open door to the bad guys, or to see if your firewall is doing what it’s supposed to do, check your ports at GRC (https://www.grc.com/x/ne.dll?bh0bkyd2). Make sure to check the Windows File Sharing and the Common Ports to see if you’re vulnerable to attack.