Chapter 1. Writing Plug-ins for Nessus

Software vulnerabilities are being discovered and announced more quickly than ever before. Every time a security advisory goes public, organizations that use the affected software must rush to install vendor-issued patches before their networks are compromised. The ease of finding exploits on the Internet today has enabled a casual user with few skills to launch attacks and compromise the networks of major corporations. It is therefore vital for anyone with hosts connected to the Internet to perform routine audits to detect unpatched remote vulnerabilities. Network security assessment tools such as Nessus can automatically detect such vulnerabilities.

Nessus is a free and open source vulnerability scanner distributed under the GNU General Public License (GPL). The Nessus Attack Scripting Language (NASL) has been specifically designed to make it easy for people to write their own vulnerability checks. An organization might want to quickly scan for a vulnerability that is known to exist in a custom or third-party application, and that organization can use NASL to do exactly that. Provided you have had some exposure to programming, this chapter will teach you NASL from scratch and show you how to write your own plug-ins for Nessus.