4.2. Preparing for Your First Scan

Running Nessus requires planning and practice. In guiding you through your first practice scanning session with Nessus, this chapter will also take you through your first planning session for a scan. The issues addressed here: Authorization, Risk vs. Benefit, Providing Authentication Information, and Plugin Selection, should be reviewed before any and every scan you perform.

4.2.1. Authorization

The most important thing to do before you launch a network scan is to obtain authorization, preferably in written form. Whom you should obtain this authorization from depends on the network you are testing; if you are planning to use Nessus on the internal network at your company, the CIO/CSO and senior administrative staff should be contacted. In the case of externally hosted systems, you might have to contact the hosting company or ISP and let them know of your intent to perform security scans against those systems. The tests that Nessus performs often look identical to a real attack by an unauthorized intruder, so make sure that the people monitoring system log files, intrusion detection systems (IDSs), and firewalls know when you are going to scan and from what address. There might be things you don't know about the network that could impact your scans. There might also be things about the network that could be impacted by your scans. If this first scan turns out to be an unannounced denial-of-service (DoS) attack, then there probably won't be a second scan.