Common Attack Pattern Enumeration and Classification
A Community Resource for Identifying and Understanding Attacks
An attacker sends out an ICMP Type 8 Echo Request, commonly known as a 'Ping', in order to determine if a target system is responsive. If the request is not blocked by a firewall or ACL, the target host will respond with an ICMP Type 0 Echo Reply datagram. This type of exchange is usually referred to as a 'Ping' due to the Ping utility present in almost all operating systems. Ping, as commonly implemented, allows a user to test for alive hosts, measure round-trip time, and measure the percentage of packet loss. Performing this operation for a range of hosts on the network is known as a 'Ping Sweep'. While the Ping utility is useful for small-scale host discovery, it was not designed for rapid or efficient host discovery over large network blocks. Other scanning utilities have been created that make ICMP ping sweeps easier to perform. Most networks filter ingress ICMP Type 8 messages for security reasons. Various other methods of performing ping sweeps have developed as a result. It is important to recognize the key security goal of the attacker is to discover if an IP address is alive, or has a responsive host. To this end, virtually any type of ICMP message, as defined by RFC 792 is useful. An attacker can cycle through various types of ICMP messages to determine if holes exist in the firewall configuration. When ICMP ping sweeps fail to discover hosts, other protocols can be used for the same purpose, such as TCP SYN or ACK segments, UDP datagrams sent to closed ports, etc. The attackers goal is to discover as many potential targets as possible can utilize a wide range of techniques to achieve this end. ICMP pings have the following characteristics:
Target Attack Surface Description
Targeted OSI Layers: Network Layer
Target Attack Surface Localities
Target Attack Surface Types: Host
Target Functional Services
Ability to send custom ICMP queries. This can be accomplished via the use of various scanners or utilities.
[R.285.1] [REF-20] Stuart McClure, Joel Scambray and George Kurtz. "Hacking Exposed: Network Security Secrets & Solutions". Chapter 2: Scanning, pp. 44-51. 6th Edition. McGraw Hill. 2009.
[R.285.2] [REF-23] J. Postel. "RFC792 - Internet Control Messaging Protocol". Defense Advanced Research Projects Agency (DARPA). September 1981. <http://www.faqs.org/rfcs/rfc792.html>.
[R.285.3] [REF-24] R. Braden, Ed.. "RFC1122 - Requirements for Internet Hosts - Communication Layers". October 1989. <http://www.faqs.org/rfcs/rfc1122.html>.
[R.285.4] [REF-28] Mark Wolfgang. "Host Discovery with Nmap". November 2002. <http://nmap.org/docs/discovery.pdf>.
[R.285.5] [REF-22] Gordon "Fyodor" Lyon. "Nmap Network Scanning: The Official Nmap Project Guide to Network Discovery and Security Scanning". Section 3.5.2 Ping Scan (-SP), pg. 58. 3rd "Zero Day" Edition,. Insecure.com LLC, ISBN: 978-0-9799587-1-7. 2008.
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