NetSonar scouts out your network flaws

Your network probably is not anywhere near as secure as it needs to be. If you subscribe to any security alert services, you know how difficult it is to keep up to date on security holes that hackers ferret out. Network security scanners take the burden off you by searching the nooks and crannies of your network to find vulnerabilities and then telling you which nodes need to be fixed. Cisco Systems Inc.'s NetSonar Security Scanner 2.0 is one scanner that we decided to add to our security toolbox.

NetSonar searches your networks and finds all the chinks in the firewalls, patches in the PCs and front-door keys under welcome mats. The software puts the information into a database, which makes it easy to analyze the data from various angles. The audit of your vulnerabilities is an eye-opening experience. But NetSonar also guides you in plugging the security holes, with a user-friendly World Wide Web-based navigation tool.

Installing NetSonar on a workstation running Microsoft Corp.'s Windows NT 4.0 took just minutes. The complex licensing process binds your copy of the software to your PC's Media Access Control address (a hardware address that identifies each node of a network), which means in practice that it can be run only on a computer that has the network interface card you used when you installed the software. So be careful which card you use during the installation, as you will be stuck with it. While this is a bothersome arrangement we would like to see changed, the good news is that you are not chained to any range of Internet Protocol addresses or to an e-mail address. Consultants and information systems administrators can place NetSonar on a laptop and take it wherever they need to go.

Anxious to see what our own network looked like, we skipped an opportunity to train on sample data and went straight to the auto discovery.

We didn't want to chance bogging down our system with network traffic, so we entered IP ranges to limit the scan to three subnets. We turned on most of the large selection of options in order to do a thorough job of pinging, nudging and probing the Transmission Control Protocol and User Datagram Protocol ports on our network. You can configure scans that will be completed in several hours or just a few minutes, and you can schedule scans to run when needed.

Cisco is considering adding an option to ensure that auto discovery doesn't use too much bandwidth, but the process placed almost no strain on our system. Our plan was to run the discovery at night when network usage was low, even though it would miss the computers that were turned off. These good intentions were foiled when our Microsoft screen saver kicked in, bringing the low-level activities of NetSonar to a halt.

The next morning we completed the run, taking nine hours of active running to scan 126 nodes. To NetSonar, a node is any PC, server, router, firewall or other device with an IP address, all of which can have security vulnerabilities.

After gathering the data, we found our way easily to the Grid Browser to look at the results.

The Grid Browser is a resizable, hyperlinked spreadsheet that enables you to view the data from many perspectives. A table of Vulnerabilities as rows and Hosts (nodes) as columns is the default grid view, and you can click Swap Axis on the toolbar to switch the classifications. You also can zoom in on sections of the table and collapse groups of columns or rows. And you easily can change individual axis views, for instance, by replacing Vulnerabilities with Operating Systems in the rows. You also can perform "data pivoting"—obtaining lists of all the hosts having a particular vulnerability, for example. All these tasks are done at the click of a mouse. The NetSonar programmers seem to have thought of everything.

We had to refer to the manual a few times to understand cryptic labels, but in an hour we had the knack of using the Grid Browser and even had generated some colorful charts and graphs illustrating our findings. We were unable to edit the labels on the graphs, many of which needed improvement, and we hope this feature will be added in future releases.

One of the first things we looked at in the Grid Browser was a table plotting operating systems in rows and Year 2000 issues in columns. At first, we were disappointed that the operating system on several PCs was shown as unknown, but then we realized that these were PCs running Windows 3.1, which would not have sent this information in response to network probes.

Likewise, NetSonar detected Windows NT 4.0 on our workstation and noted that it should be made Year 2000-compliant by application of a service pack, but it was unable to detect that the Service Pack had already been installed.

We applaud Cisco for providing as much information as it did. After all, there is no magical way for NetSonar to take over PCs during an automated run to scan them thoroughly for Year 2000 issues. Where NetSonar finds a possibility of a security flaw but cannot confirm it, it notes the potential problem.When we knew which PCs had particular vulnerabilities, we started hyperlink jumps from the Grid Browser to the Network Security Database. This is a Hypertext Markup Language-based repository of information on security vulnerabilities and how to remedy them. Navigation was easy, and we were able to use our favorite Web browser. To keep from being overwhelmed by the amount of information, we concentrated on the flaws labeled as highest priority.

Finally we used the report wizard to construct an Executive Report. The software provides many options for building the report, and we were even able to include charts. The report is in HTML format with hyperlinks and looks good as a printed report.

If you buy NetSonar, be sure to purchase a year's subscription of download security signatures in order to detect the most recently uncovered security flaws. The prices of NetSonar and the update service are reasonable, especially considering that the experts in white-hat hacking who maintain the security database don't come cheap.

And remember that while network scanners are useful, they are only one part of a complete security toolkit. Also consider purchasing a software tool to detect and intercept network intrusions in real time, such as Cisco's NetRanger.

-- Greer is a senior network analyst at a large Texas state agency. He can be reached at

***NetSonar Security Scanner 2.0—B+Cisco Systems Inc.(800)

Price and AvailabilityAvailable on the open market for $495 for a license for 2,500 live nodes. A one-year update subscription is available for $150.

RemarksWhile there are a few rough spots in the user interface, a high level of network expertise is not required to use NetSonar. It does a thorough job of scanning networks for vulnerabilities to intrusion and of showing you how to plug the network security holes. Take advantage of the new low price, and put it into your security toolkit. It supports Microsoft Corp.'s Windows NT 4.0 and Sun Microsystems Inc.'s SPARC Solaris and Solaris x86 platforms.


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