Paywall
A paywall is a method of restricting access to content via a paid subscription. Beginning in the mid-2010s, newspapers started implementing paywalls on their websites as a way to increase revenue after years of decline in paid print readership and advertising revenue. In academics, research papers are often subject to a paywall and are available via academic libraries that subscribe.
Shorewall
It is not a daemon since it does not run continuously, but rather configures rules in the kernel that allow and disallow traffic through the system. Shorewall is configured through a group of plain-text configuration files and does not have a graphical user interface, though a Webmin module is available separately. A monitoring utility packaged with Shorewall can be used to watch the status of the system as it operates and assist in testing.