IT pros need to understand IP scanning as well as hackers do -- here's how

Use this chapter from O'Reilly's Network Security Assessment to learn the various forms of IP network scanning and how to use some of the most powerful scanning tools.

One of the best advantages that a hacker has is the ability to find system vulnerabilities that IT professionals have not already pinpointed. Hackers typically accomplish that by using a variety a IP scanning tools. This sample chapter from O'Reilly's Network Security Assessment helps even the playing field for IT pros by revealing the details of IP network scanning and demonstrating how to use a variety of powerful tools.

Author Chris McNab explains, "After undertaking initial reconnaissance to identify IP address spaces of interest, network scanning builds a clearer picture of accessible hosts and their network services. Network scanning and reconnaissance is the real data gathering exercise of an Internet-based security assessment. The rationale behind IP network scanning is to gain insight into the following elements of a given network:

• ICMP message types that generate responses from target hosts
• Accessible TCP and UDP network services running on the target hosts
• Operating platforms of target hosts and their configuration
• Areas of vulnerability within target host IP stack implementations (including sequence number predictability for TCP spoofing and session hijacking)
• Configuration of filtering and security systems (including firewalls, border routers, switches, and IDS sensors)

Performing both network scanning and reconnaissance tasks paints a clear picture of the network topology and its security mechanisms. Before penetrating the target network,further assessment steps involve gathering specific information about the TCPand UDP network services that are running, including their versions and enabledoptions."

Title: Network Security Assessment
ISBN: 059600611X
Published: March 2004
Author: Chris McNab
Chapter: Chapter 4: IP Network Scanning
Publisher: O'Reilly