ServerBuddies Support Blog

nmap - Network exploration tool and security / port scanner

Nmap (“Network Mapper”) is an open source tool for network exploration and security auditing. It was designed to rapidly scan large networks, although it works fine against single hosts. Nmap uses raw IP packets in novel ways to determine what hosts are available on the network, what services (application name and version) those hosts are offering, what operating systems (and OS versions) they are running, what type of packet filters/firewalls are in use, and dozens of other characteristics. While Nmap is commonly used for security audits, many systems and network administrators find it useful for routine tasks such as network inventory, managing service upgrade schedules, and monitoring host or service uptime.

A typical Nmap scan is shown in Example 1. The only Nmap arguments used in this example are -A, to enable OS and version detection,script scanning, and traceroute; -T4 for faster execution; and then the two target hostnames.

Example 1. A representative Nmap scan

Nessus full-service security scanner

nessus - Remote network security auditor, the client

Nessus is a full-service security scanner. The plug-in architecture of Nessus allows users to customize it for their systems and networks. As with any scanner, Nessus is only as good as the signature database it relies upon. Fortunately, Nessus is frequently updated and features full reporting, host scanning, and real-time vulnerability searches. Remember that there could be false positives and false negatives, even in a tool as powerful and as frequently updated as Nessus.

For more information about Nessus, refer to the official website at the following URL: http://www.nessus.org/

Prerequisites

Tenable recommends a minimum of 256MB of memory to operate Nessus on a local “Class C” network. To conduct larger scans of multiple networks, at least 1 GB of memory is recommended, but it can require up to 4 GB

Installation on Red Hat and SUSE

Download the latest version of Nessus from http://www.nessus.org/download/.

Nessus is available for Red Hat ES 3, ES 4, and Fedora Core 4, and SUSE 9.3 and 10.0. Unless otherwise noted, all commands should be performed as the system’s root user.

Then, install it with the following command depending on your version:

This will install Nessus into the directory /opt/nessus/.

Below is an example of the screen output for installation on Red Hat ES3:

Please run /opt/nessus/sbin/nessus-adduser to add an admin user

Register your Nessus scanner at http://www.nessus.org/register/ to obtain
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