nft:tldr:79a99

This command is using the nft command-line tool with the add rule option to add a new rule to the network filtering table.

• sudo: This command is executed with superuser (root) privileges.
• nft: It is the command-line tool used to manage the Netfilter firewall rules in the Linux kernel.
• add rule: This option is used to add a new rule to the specified table.
• ${inet}: This specifies the network family or address family. It usually represents the IPv4 or IPv6 family.
• ${filter}: This specifies the table name. In this case, it is the filter table used for packet filtering.
• ${input}: This specifies the chain within the table where the rule should be inserted. In this case, it is the input chain used for processing incoming packets.
• ${tcp}: This specifies the protocol that the rule should apply to. In this case, it is the TCP protocol.
• ${dport { telnet, ssh, http, https } accept}: This specifies the rule itself. It matches packets with a destination port number matching any of the specified ports (telnet, ssh, http, https) and accepts them.

In summary, this command adds a new rule to the filter table's input chain that accepts TCP packets with the destination port number matching telnet, ssh, http, or https.