Vulnerability scanning: It's all about control

We are used to fake computer effects, so we were astonished to see Trinity use a real-life port scanner in the movie "The Matrix: Reloaded" and then execute a hack that actually could have worked against a real computer. Fortunately, the bad guys had not applied the latest security patches.

A vulnerability scanner is the best tool for ensuring that all of your users are following security policies and applying all the patches. We decided to test Qualys Inc.'s QualysGuard Intranet Scanner because it was the first appliance-based vulnerability assessment tool and we wanted to see how well its Web-based management worked.

We also wanted to compare QualysGuard with Nessus Security Scanner from the Nessus Project. There are many vulnerability scanners on the market, but Nessus is popular because it is free and has undeniably good features.

Installing QualysGuard was about as easy as popping the five-pound appliance into a rack and turning it on. The average systems administrator should be able to get it up and running within 15 minutes. Compare that with two hours or more for a competent Linux user to properly configure and install Nessus.

Another advantage of the QualysGuard appliance is that it is designed to automatically keep signature files updated and run recurring scans. Administrators using Nessus must configure the server to provide those functions.

By the way, because of a significant increase in hacker activity during the past few months, we believe vulnerability audits should be conducted every month, if not more often.

We first turned the QualysGuard appliance against itself, trying to find any overlooked vulnerabilities. After trying to break in, we concluded that the Linux system running on the appliance had been masterfully hardened against intrusions. A Qualys technician later told us that even if we had managed to get root access, we still would not have been able to tamper with the operating system.

If you rely on Nessus, it is up to you to harden your Linux or Unix server against attack. We recommend the book "Securing and Optimizing Linux," available at bookstores or as a 486-page free PDF download at www.linux security.com. Stripping out unnecessary daemons and tools and implementing all the steps necessary to secure your network will take a considerable amount of time. Even then, you will still have to keep security patches up-to-date — a process that Qualys has automated on its scanner.

To give QualysGuard a good workout, we used a subnetwork with 240 computers — a mix of Microsoft Corp. Windows 9x/2000 workstations, Windows NT 4/2000 servers, Novell Inc. NetWare 5/6 servers and a few Linux machines.

After entering an IP range for our subnet, we began mapping and scanning operations. Within five hours, we had a finished report. Even though more than 1,500 vulnerabilities were found across all the machines, the report was so well organized that we did not feel overwhelmed with data.

The first part of the report was an executive overview complete with colorful charts and graphics. The current Nessus Linux and Unix client software has only limited graphics, and the Nessus Windows client has none at all.

Both QualysGuard and Nessus arrange reports by the industry-standard list of Common Vulnerabilities and Exposures (see www.cve.mitre.org for more information). We recommend against buying any product that does not comply with that standard.

Although Qualys claims to be able to detect a large number of vulnerabilities, in our results, Nessus listed a few more items than QualysGuard. However, we preferred the QualysGuard report, because it had fewer unnecessary informational items and was more focused on how security administrators would actually use the report. In the past, we've encountered vulnerability scanner reports that were too bulky to be worthwhile.

The QualysGuard reports seem to use the highest threat levels of "urgent" and "critical" more sparingly than other scanner products, and we appreciate this concentration on the important issues. The QualysGuard choices of threat levels for each vulnerability seemed more consistent than those of Nessus, in which different people write the software used to detect specific problems.

We were impressed that both QualysGuard and Nessus detected a Code Red worm on one of our Web servers, while our antivirus software did not.

QualysGuard produces reports in HTML, Web archive and Extensible Markup Language formats; Nessus reports are available in HTML, plain text and PDF.

QualysGuard includes a network-mapping tool that can only be described as cool. This feature can create a detailed map of your network in a relatively short time. Hosts on the network are logically and neatly organized by router. If your network is large, be prepared for a cluttered map. But frankly, we have never used a network-mapping product that could display 250 or more hosts without cluttering the screen. Subnets can be hidden from view to simplify analysis, and hosts can be filtered by operating system, discovery method, IP range or myriad other parameters, giving the administrator a picture of only what is important.

If your organization is in the market for a network-mapping program, it may be possible to fill this need with QualysGuard and help justify some of the scanner's cost. Nessus does not include a mapping feature.

In our QualysGuard reports, the NetWare 5.1 servers were incorrectly identified as 6.0. Qualys' technical support staff resolved the problem within 48 hours. Applying NetWare Service Packs 4 and 5 gives NetWare 5.1 the same "fingerprint" as NetWare 6.0. QualysGuard now reports these versions as NetWare 5/6.

We found that the QualysGuard appliance can only be managed by logging into a Web site maintained by Qualys. Under the fee model, you are charged only for the IP addresses you scan. Before any hosts can be scanned, you must enter IP information, and you can delete and modify IP ranges and domains. But you are not allowed to delete individual IP addresses, although these can be removed by contacting the Qualys account manager. Nessus, of course, has no restrictions on which machines are scanned.

If your agency needs fast setup, low maintenance and scalable performance and has the budget to buy the best, QualysGuard is for you.

Greer and Bishop are network analysts at a large Texas state agency. They can be reached at Earl.Greer@dhs.state.tx.us.