Which of the following is used to gather information about a remote network protected by a firewall?

Warchalking involves drawing symbols in physical locations to indicate nearby wireless network availability and has no relevance to firewall rule enumeration.

Wardialing automates dialing large ranges of phone numbers to discover modems or fax machines and does not apply to firewall-protected IP networks.

Firechalking is not a recognized security technique or tool in any standard security reference.

Firewalking sends probe packets with a TTL calibrated to expire exactly one hop beyond the firewall - if a port is open the packet reaches the target host and may elicit a response, whereas closed or filtered ports yield no response or an ICMP error, allowing the attacker to map the firewall's access control rules. This technique specifically enables reconnaissance of remote networks protected by firewalls without requiring direct access to the defended segment.