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We have touched on many of the more common vulnerabilities found in today's computing environment. There are numerous other vulnerabilities associated with operating systems and applications. We have seen a common theme in our recommended procedures to deal with each vulnerability—monitor for and install system patches as they become available. Each month between 20 and 70 new vulnerabilities are published on the Internet. There is a critical time period between the publication of the vulnerability and the application of the patch that needs to be managed. In addition, security monitoring of intrusion detection systems and system logs can detect attacks as they occur and enable the organization to respond accordingly. Appropriate incident response procedures may prevent the attack from being successful or may help to minimize and contain any potential damage.
While vendors are generally responsive in publishing newly discovered vulnerabilities and the patches or procedures to address them, system administrators do not have time to visit each vendor Web site on a daily or even weekly basis. There are mailing lists such as CERT, Bugtraq, and others that will notify subscribers as new vulnerabilities are published. However, the e-mails cover all systems and can be overwhelming to read and sort through. Fortunately, there are services to help system administrators monitor and locate system patches. Vulnerability subscription services provide information on the new vulnerabilities as they become published. The level of information included with the services varies from a straight listing of vulnerabilities to searchable databases to customized profiles that e-mail you when a new vulnerability affecting your profile is published. Subscribing to or monitoring one of these services is the only way to keep up to date with emerging vulnerabilities. There are several free services that publish new vulnerabilities as they are found. Sites such as Security Focus (www.securityfocus.com), eSecurityonline (www.esecurityonline.com), and the Computer Security Division of the National Institute for Standards and Technologies (NIST) ICAT (http://csrc.nist.gov/icat/) site, pictured in Figure 4-2, contain searchable databases of vulnerabilities. Searchable databases enable administrators to look for new vulnerabilities related to products they use. Many of the databases enable a user to search by operating system, application, severity, date, and other fields.
While these searchable vulnerability databases provide a starting point for system administrators trying to track new vulnerabilities, they do not completely solve the problem. One of the biggest problems for the system administrator trying to monitor newly emerging vulnerabilities is time. Even using sites that e-mail vulnerabilities tends to overwhelm administrators with e-mail of vulnerabilities that do not pertain to the systems under their control. Using services that are customizable and notify system administrators when a new vulnerability emerges that affects their systems is a way administrators can save time in addressing vulnerabilities on a regular basis.
Cutting down on the work involved with vulnerability monitoring is a step in the right direction. However, to eliminate the exposures to new vulnerabilities, an enforcement mechanism is needed to validate that identified vulnerabilities are addressed and repaired in a timely manner. Testing using the techniques and tools described in this book is one method of enforcement. Even these steps require quite a bit of structure and coordination to be effective over time. Automated security scans and monitoring cut down on the time required to determine whether security exposures have been addressed. Regular scans using tools such as Cybercop, ISS Internet Scanner, or Nessus will help in this area. Configuration management tools such as Symantec's Omniguard Enterprise Security Manager (ESM) provide another enforcement mechanism. These tools are not cheap, but the implications of not plugging security holes regularly are not cheap either. Vulnerability scanning tools are discussed in further detail in Chapter 11.
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