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
Shorewall is mainly used in network installations (as opposed to a personal computer firewall), since most of its strength lies in its ability to work with "zones", such as the DMZ or a 'net' zone. Each zone would then have different rules, making it easy to have for example relaxed rules on the company intranet, yet clamp down on traffic coming in from the Internet.