There was a time when home computer users were worried about hackers getting into their computer and therefore the firewall software was designed for monitoring the in-bound network or internet traffic. Now situation has become entirely different. Now you have to monitor everything including the outbound connections – applications sending data from your computer to the internet.
If you are using macOS then you can use a small software called “Little Snitch” that can do this for you. It is a “reverse firewall” for macOS. It monitors only the processes that want to send data from your computer to the Internet. This way you can keep an eye on the data and the programs trying to steal your private information that may reveal your user identity such as your location or how you use your computer.
Little snitch is very useful in the case you are already infected with some sort of malware or spyware. If such malicious software is regularly sending your user data to a server on the internet, then Little Snitch can easily block it from doing so. Since this program blocks the access of programs on your computer from sending data outside, Little Snitch is being called a reverse firewall.
When an app tries to connect to the internet, Little Snitch shows an alert on your screen. You can take the decision whether you want to allow the connection or you want to block it from connecting to the internet. If you do no want to see so many alerts form Little Snitch, you can put it in the silent mode which postpones the alerts for a while and lets you make the decision at a later time. This silent mode is useful for when you are busy doing something important and do not want to be bothered by all these disturbances.
Little Snitch is good for keeping all the outbound traffic in check on your Mac. It is not free and is available only in a 30 day trial version. If you are not using any other security software, then it can provide you some level of security and full control over which programs are connecting to the internet.
You can download Little Snitch for macOS from https://www.obdev.at/products/littlesnitch/.