There are tens of thousands of ports for every IP address, and a hacker who knows your IP can try to brute-force a connection. Once they succeed, hackers can take control of your device, steal your data or even impersonate you.
O&O ShutUp10 is entirely free and does not have to be installed – it can be simply run directly and immediately on your PC. And it will not install or download retrospectively unwanted or unnecessary software, like so many other programs do these days!
Finding out a password is the usually the first step in cracking a network's security. (That's why there are so many articles telling you to change your passwords often and make them hard to figure out!)