Active Reconnaissance of External and Internal Networks

The main goal of the active reconnaissance phase is to collect and weaponize the information about the target as much as possible in order to facilitate the exploitation phase of the kill chain methodology.

We have seen how to perform passive reconnaissance using OSINT, which is almost undetectable, and can yield a significant amount of information about the target organization and its users.

Active reconnaissance builds on the results of OSINT and passive reconnaissance, and emphasizes more focused probes to identify the path to the target and the exposed attack surface of the target. In general, complex systems have a greater attack surface, and each surface may be exploited and then leveraged to support additional attacks.

Although active reconnaissance produces more useful information, interactions with the target system may be logged, triggering alarms by protective devices, such as firewalls, Intrusion Detection Systems (IDS), and Intrusion Prevention Systems (IPS).

As the usefulness of the data to the attacker increases, so does the risk of detection; this is shown in the following diagram:

To improve the effectiveness of active reconnaissance in providing detailed information, our focus will be on using stealthy, or difficult to detect, techniques.

In this chapter, you will learn about the following topics:

• Stealth scanning strategies
• External and internal infrastructure, host discovery, and enumeration
• The comprehensive reconnaissance of applications, especially using recon-ng
• The enumeration of internal hosts using DHCP
• Useful Microsoft Windows commands for penetration testing
• Taking advantage of default configurations