If you're looking for an easy, cost-effective way of system discovery on your network, look no further than OpenVAS.
As a network administrator, it's crucial that you know what machines are on your network. With the results of such a scan, there are numerous actions you can take. Without that scan, you might not be aware of what's currently on your network (or what IP address is taken by what system).
OpenVAS is an outstanding piece of software that makes the process of scanning your network incredibly simple. I've already walked you through the process of installing OpenVAS (See: Learn how to install the open source security audit tool, OpenVAS, on the Ubuntu Server platform). Now I'm going to walk you through the steps of running a complete network scan.
SEE: Server deployment/migration checklist (Tech Pro Research)
What you need
The only things you need is a working instance of OpenVAS (which is connected to the network you want to scan), an admin account for OpenVAS, and the IP address scheme of your network.
With those things in hand, let's scan.
Creating the scan
The first thing you need to do is log into OpenVAS with an admin account. Once authenticated, click on Scans | Tasks (Figure A).
In the resulting window (Figure B), click on the star icon in the upper left corner and then click New Task.
An overlay window will appear (Figure C). In this window, give the new scan a name and comment. Next click on the star icon to the right of Scan Targets, which will open yet another pop-up window.
Think of a target as either a single machine, a group of machines, or an entire network of machines. In the New Target popup (Figure D), give the target a name and comment, and then type the IP address or IP address range (as in 192/168.1.1/24) in the IP address window. If you have SSH-enabled hosts, click the star button associated with SSH and, in the resulting window, fill out the necessary information for your SSH credentials and click Create. Once you've created the necessary SSH credentials entry, select it from the SSH dropdown, and click Create.
Note: You can also create credentials for SMB, ESXi, and SNMP in the same fashion.
You will then be taken back to the New Task window, where you can continue to configure the task to meet your needs. Since we're doing an initial network scan, select System Discovery from Scan Config and click Create.
Back at the Tasks window, click the run button (right-pointing green arrow--Figure E) associated with the new task. This will fire off the network scan. Depending on how large your network is, the task can take considerable time. I've run scans with this tool, which have taken hours to complete, so give it the time it needs.
When the scan completes, click Scans | Reports to view the results of your scan. Select the scan you just ran to gain access to the report.
Congratulations, you've just run your first network discovery scan, using OpenVAS.
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