Which command adds a new IP address to the BlockThem IPset?

The command that successfully adds a new IP address to an IPset is "ipset add". This command is specifically designed to add an element, such as an IP address, to an IPset defined in Linux.

When using "ipset add," you would typically follow it with the name of the IPset and the IP address you wish to add. For instance, if you have an IPset named BlockThem, the command would look like this: ipset add BlockThem <ip_address>. This straightforward syntax allows users to efficiently manage IPsets for firewall configurations, network security, and other possible use cases.

The other choices provided do not accurately describe the correct usage of commands associated with managing IPsets. They either reflect non-existent commands, improper usage, or are variations that don't align with the expected syntax in the ipset utility. Understanding the specific command structure is crucial for effectively utilizing IPsets in Linux networking contexts.