Evaluating the Tools
A typical assessment can start by using some form of information gathering tool. If assessing the entire network, map the network layout first to find the hosts that are running. Once located, we can then focus on examining them. Focusing on these hosts will require another set of tools. Knowing which tools to use may be the most crucial step in finding vulnerabilities.
Just as in any aspect of everyday life, there are many different tools that perform the same job. This concept applies to performing vulnerability assessments as well. There are tools specific to operating systems, applications, and even networks (based on protocols used). Some tools are free (in terms of cost) while others are not. Some tools are intuitive and easy to use, while others are cryptic and poorly documented.
Deciding which tools are the right tools for you may be a daunting task. In the end, experience counts. If possible, set up a test lab and try out as many tools as you can, noting the strengths and weaknesses of each. Review the README file or man page for the tool. In addition, look to the Internet for more information, such as articles, step-by-step guides, or even mailing lists specific to a tool.
The tools discussed below are just a small sampling of the available tools.
Scanning Hosts with Nmap
Nmap is a popular tool for mapping networks is included in Red Hat Linux. Nmap has been available for many years and is probably the most often used tool when gathering information. An excellent man page is included that covers the details, options, and examples of using Nmap. Use it on your network to find host systems and open ports on those systems.
Nmap is a competent first step in vulnerability assessment. You can map out all the hosts within your network, and even pass an option that will allow it to attempt to identify the operating system running on those hosts. Nmap is a good foundation for establishing a policy of using secure services and stopping unused services.
Using Nmap
Nmap can be run from a shell prompt or using a graphical version. At a shell prompt, type the nmap command followed by the hostname or IP address of the machine you want to scan.
nmap foo.example.com |
The results of the scan (which could take up to a few minutes, depending on where the host is located) should look similar to the following:
nmap 127.0.0.1 Starting nmap V. 3.00 ( www.insecure.org/nmap/ ) Interesting ports on localhost.localdomain (127.0.0.1): (The 1591 ports scanned but not shown below are in state: closed) Port State Service 22/tcp open ssh 25/tcp open smtp 111/tcp open sunrpc 515/tcp open printer 950/tcp open oftep-rpc 6000/tcp open X11 Nmap run completed -- 1 IP address (1 host up) scanned in 0 seconds |
If you were to use the graphical version (which can be run by typing /usr/bin/nmapfe at a shell prompt), the results will look similar to the following:
Nmap tests the most common network communication ports for listening or waiting services. This knowledge can be helpful to an administrator who wants to, for example, close down unnecessary services.
For more information about using Nmap, refer to the official homepage at http://www.insecure.org.
Nessus
Nessus is a full-service security scanner. The plug-in architecture of Nessus allows users to customize it for their systems and networks. As with any scanner, Nessus is only as good as the signature database it relies upon. Fortunately, Nessus is updated on a daily basis. It features full reporting, host scanning, and real-time vulnerability searches. Remember that there could be false positives and false negatives, even in a tool as powerful and as frequently updated as Nessus.
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Nessus is not included with Red Hat Linux and is not supported. It has been included in this document as a reference to users who may be interested in using this popular application. |
For more information about Nessus, refer to the official website at http://www.nessus.org.
Whisker
Whisker is an excellent CGI scanner. Whisker has the capability to not only check for CGI vulnerabilities but do so in an evasive manner, so as to elude intrusion detection systems. It comes with excellent documentation which should be carefully reviewed prior to running the program. When you have found your Web servers serving up CGI scripts, Whisker can be an excellent resource for checking the security of these servers.
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Whisker is not included with Red Hat Linux and is not supported. It has been included in this document as a reference to users who may be interested in using this popular application. |
More information about Whisker can be found at http://www.wiretrip.net.
VLAD the Scanner
VLAD is a scanner developed by the RAZOR team at Bindview, Inc. that may be used to check for vulnerabilities. It checks for the SANS Top Ten list of common security issues (SNMP issues, file sharing issues, etc.). While not as full-featured as Nessus, VLAD is worth investigating.
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VLAD is not included with Red Hat Linux and is not supported. It has been included in this document as a reference to users who may be interested in using this popular application. |
More information about VLAD can be found on the Tools page on the RAZOR team website at http://razor.bindview.com/index.shtml.
Anticipating Your Future Needs
Depending upon your target and resources, there are any number of tools available. There are tools for wireless networks, Novell networks, UNIX systems, Linux systems, and more. Another essential part of performing assessments may include reviewing physical security as well as war dialing — dialing numbers and extensions enterprise-wide for modem access to your network. New concepts, such as war walking — scanning the perimeter of your enterprise's physical structures for wireless network access — are some emerging concepts that you can investigate and, if needed, incorporate in your assessments. Imagination and exposure are the only limits of planning and conducting vulnerability assessments.