To extend on How can a webpage scan my local, internal network from the Internet? how safe is my private network against possible threats like DoS attacks, spoofing attacks, revealing info about my private network services etc. Have there have been recent exploits?
I recently read (https://www.sans.org/reading-room/whitepapers/networkdevs/easy-steps-cisco-extended-access-list-231) that without an ACL set incoming ICMP echo request (ICMP type 8), ICMP time-exceeded (ICMP type 11) could reveal your intranet structure. Is that true?