MacOS – Little Snitch uninstalled properly but Little Snitch Helper still here

No.

If, for all processes.

Pretty much yes.

If, only for web browsing.

As @StuWilson has pointed out, port 80 is for http traffic and port 443 is for https traffic. (http with TLS/SSL encryption).

It's not necessary to allow all traffic of all processes on port 80. But - for the sake of comfortable browsing - I strongly recommend enabling those ports for all traffic of webbrowsers like Safari or Chrome.

For comparison, this is my setup of Chrome in HandsOff!:

• Basic communication

  • Allow all outgoing network connections on port 443 (https)
  • Allow all outgoing network connections on port 80 (http)
  • Allow all domain resolving

• Sync

  • Allow all outgoing network connections to talk.google.com on port 5222

• Other (e.g. media)

  • Allow all outgoing network connections to atracktive.collegehumor.com on port 9090 (websm)
  • ...

Setting up a firewall can be quite a hassle. Generally - when I've expected a certain connection to build up, and know what it's for, I allow it. But you should only interfere network connections when you know what you're doing.

Many system processses regulary build up (local) network connections that are certainly valid. If you don't know how to guard a firewall, you become the first security risk for your own computer. Make sure to educate yourself on network protocols when building your own firewall.

Little Snitch will tell you and allow you to do the following:

• Informs you when an app or process trys to access "stuff" over the network
• Allows you to set up and block communication by one of more of the following:
  • Protocol
  • Port
  • App or Process
  • destination address, IP address, or hostname, and more.

Unfortunately what it does not allow you to do is filter or create rules based on the "Location" or the current connection name as defined in OS X Network preferences (with the exception of "Local Network")

Other Firewall Software may allow you to do this, but this is a limitation of Little Snitch.

Littel Snitch 3 is now in preview mode, one among the new features is "Profiles" defined as follows:

Profiles

With Little Snitch 3, rules can optionally be arranged in separate profiles like “Home”, “Office” or “Internet Cafe”. Rules that are assigned to a particular profile are only effective if that profile is active. The active profile can be chosen conveniently from the status menu.

This allows you to quickly switch between different sets of rules depending if you are at home, at the office or connected to a public network.