Scanning the Horizon

How secure is your enterprise network? Today that’s a harder question to answer than ever, especially as enterprise networks continue to grow in size and complexity.

Just consider: the number of security incidents is mushrooming each year, “critical” software patches are issued every month, and attacks move with such speed that companies scarcely have time to respond to them. This summer’s Blaster worm, for example, arrived just 26 days after Microsoft disclosed an RPC DCOM Windows flaw and released a patch. That’s why knowing the ins and outs of your network infrastructure has never been more mission-critical than it is now.

For many enterprises, providing a “deep look” into the network is the job of a vulnerability assessment scanner. This tool can root out possible weak points in a network before attackers do. For example, a scanner can probe networks for known vulnerabilities in operating systems, applications, and passwords, to name just a few areas. A scanner can also use sophisticated path analysis to illustrate the exact sequence of steps an intruder might take to discover and exploit a vulnerability in the network.

Let’s look at the key features of a vulnerability assessment scanner and how to get the most out of this essential tool.

‘What can a hacker see?’

Until a few years ago, many businesses were generally safe from Internet intrusions because they relied on dial-up connections. (Dial-up connections via phone lines receive a different Internet address on every call and are open too briefly to give hackers reliable access.) But today’s broadband connections have Internet addresses that remain the same either permanently or for hours at a time. Once hackers find their way into a vulnerable network, they can explore or damage it at their leisure. Keep in mind, too, that your network may not be the real object of a hacker’s plans. Distributed denial of service attacks have been launched from innocent third-party networks that were hijacked by hackers using clandestine intrusion attacks.

A vulnerability assessment scanner takes a hacker’s view of the network. It automatically scans systems and services on the network and simulates common intrusion or attack scenarios. In essence, it answers the question, “What can a hacker see and exploit on the network?” (In contrast, so-called host-based scanners assess system-level vulnerabilities such as file permissions, user account properties, and registry settings.) Therefore, a vulnerability assessment scanner should be capable of:

  • Safely testing the entire network for security vulnerabilities and providing recommendations on how to fix them
  • Scanning multiple operating systems, including Unix, Linux, Windows 2000, and NetWare
  • Staying current with the very latest vulnerability signatures and alerts
  • Displaying scan progress with a real-time graphic view, revealing the root cause of vulnerabilities
  • Providing customizable management reports for a range of audiences

The importance of a scanner keeping current with the latest vulnerabilities cannot be underestimated. Successful defense against the new generation of blended threats – such as Slammer and Code Red — requires a combination of steps and security functions. This includes use of an antivirus product, firewall technology, a security policy compliance tool (for identifying inadequate patch levels, finding unneeded services, and discovering weak passwords), intrusion protection solutions, as well as a vulnerability assessment scanner. Blended threats are expected to appear with increased regularity and growing complexity, and an integrated strategy represents an enterprise’s best bet to address security at each tier of the network (i.e., client, server, and gateway).

Scanning and reporting

A comprehensive vulnerability scan begins by “discovering” all of the active devices on the network. This is followed by a port scan, which identifies ports in listening mode as well as those that may have exploitable active services. Full scans check for open TCP and UDP ports and examine network services (such as DNS and FTP). These scans will also check operating systems and application software for unauthorized modifications and for known problems that can be fixed by patches.

Next, the scanner analyzes the data and generates a report detailing potential vulnerabilities and fixes. A scanner should display data in real time as it scans, then provide appropriate reports so administrators don’t have to search through volumes of data. Beware of scanners that flood you with hundreds of pages of potential problematic symptoms (or too many “false positive” reports). A scanner should illustrate the cause of a problem, the risk it poses, and make recommendations on how to eliminate it. As for the reports themselves, you should be able to tailor them for a range of audiences, both technical and executive, and be able to export them to a variety of formats, such as Word, Excel, and HTML.

In or out?

Several factors must be considered if you plan to undertake vulnerability assessment scanning, including whether to do the job in-house. Today companies are increasingly considering turning to a managed security services provider (MSSP) to handle the task. Any organization considering partnering with an MSSP should first ask the following questions:

  • Does the MSSP under consideration have sufficient consultants to assist onsite and to assist in implementing any recommendations?
  • Does the provider or its partners have the national or global reach required by your company?
  • Does the provider have sufficient financial wherewithal to survive varying economic climates?

Timeliness is key

Regardless of whether the job is done in-house or through a partnership, security experts agree that once a vulnerability assessment has been performed, it’s important to take corrective action promptly. If too much time passes between when the scanning occurs and when corrective action is taken, network connections might change, rendering your report out of date.

Remember, too, that vulnerability assessment scanning is not a one-time fix. A security edifice that is rock-solid today can crumble tomorrow under the assault of newly discovered exploits. (And that’s all the more reason to make sure that the scanner you select keeps current with the latest vulnerabilities.) Security experts recommend that you run penetration tests against critical sites every three months. It is also suggested that you change penetration testers every six months to provide a breadth of vulnerability analysis.

It should also be emphasized that vulnerability assessment scanning does not replace in-person security audits. Your company’s enterprise security policies and procedures need to be regularly reviewed by actual persons to guarantee that they are in place and being followed. The bottom line: effective security is a combination of people, policies, procedures, and technologies.


Protecting today’s dynamic networks against ever-changing security threats requires vigilance as well as action. A vulnerability assessment scanner, frequently updated to reflect the latest attacks, can be an essential weapon in your information security arsenal. The recent Blaster worm was just the latest reminder that corporations need to move swiftly to prevent attack. It won’t be the last.

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