If a server runs a modified version of the TCP connection handling code, what technique can it use to defend against a SYN spoofing attack? Select one: a. Check the Assigned Numbers RFC to ensure that the sender is not using a spoofed IP address b. Send an ICMP Protocol Unreachable message and request that the client use UDP instead of TCP c. Use packet filtering to verify that the IP address is not spoofed d. Send a cryptographically encoded cookie in its SYN/ACK and require the client to return the cookie