WHAT IS FOOTPRINTING?

The systematic and methodical footprinting of an organization enables attackers to create a complete profile of an organization's security posture . By using a combination of tools and techniques coupled with a healthy dose of patience, attackers can take an unknown entity (for example, XYZ Organization) and reduce it to a specific range of domain names , network blocks, and individual IP addresses of systems directly connected to the Internet, as well as many other details pertaining to its security posture. Although there are many types of footprinting techniques, they are primarily aimed at discovering information related to the following environments: Internet, intranet, remote access, and extranet. Table 1-1 depicts these environments and the critical information an attacker will try to identify.

Table 1-1: Environments and the Critical Information Attackers Can Identify

Technology	Identifies
Internet	Domain name Network blocks Specific IP addresses of systems reachable via the Internet TCP and UDP services running on each system identified System architecture (for example, Sparc vs. x 86) Access control mechanisms and related access control lists (ACLs) Intrusion-detection systems (IDSs) System enumeration ( user and group names, system banners, routing tables, and SNMP information) DNS hostnames
Intranet	Networking protocols in use (for example, IP, IPX, DecNET, and so on) Internal domain names Network blocks Specific IP addresses of systems reachable via the intranet TCP and UDP services running on each system identified System architecture (for example, SPARC vs. x 86) Access control mechanisms and related ACLs Intrusion-detection systems System enumeration (user and group names, system banners, routing tables, and SNMP information)
Remote access	Analog/digital telephone numbers Remote system type Authentication mechanisms VPNs and related protocols (IPSec and PPTP)
Extranet	Connection origination and destination Type of connection Access control mechanism

Why Is Footprinting Necessary?

Footprinting is necessary to systematically and methodically ensure that all pieces of information related to the aforementioned technologies are identified. Without a sound methodology for performing this type of reconnaissance, you are likely to miss key pieces of information related to a specific technology or organization. Footprinting is often the most arduous task of trying to determine the security posture of an entity; however, it is one of the most important. Footprinting must be performed accurately and in a controlled fashion.