A Few Good Information Security Metrics

Andrew Jaquith says information security metrics don't have to rely on heavy-duty math to be effective, but they also don't have to be dumbed down to red, yellow, green. Here are five smart measurements--and effective ways to present them.

Try these advanced versions: You can parse coverage percentages according to several secondary variables. For example, percentage coverage by class of device (for instance, 98 percent antivirus coverage of desktops, 87 percent of servers) or by business unit or geography (for instance, 92 percent antispyware coverage of desktops in operations, 83 percent of desktops in marketing) will help uncover tendencies of certain types of infrastructure, people or offices to miss security coverage. In addition, it's a good idea to add a time variable: Average age of antivirus definitions (or antispyware or firewall rules and so on). That is, 98 percent antivirus coverage of manufacturing servers is useless if the average age of the virus definitions on manufacturing's servers is 335 days. A star company, Jaquith says, will have 95 percent of their desktops covered by antivirus software with virus definitions less than three days old.

One possible visualization: Baseline defenses can be effectively presented with a "you are here" (YAH) graphic. A YAH needs a benchmark—in this case it's the company's overall coverage. After that, a business unit, geography or other variable can be plotted against the benchmark. This creates an easy-to-see graph of who or what is close to "normal" and will suggest where most attention needs to go. YAHs are an essential benchmarking tool. The word "you" should appear many times on one graphic. Remember, executives aren't scared of complexity as long as it's clear. Here's an example: plotting the percentages of five business units' antivirus and antispyware coverage and the time of their last update against a companywide benchmark.

metric 2: Patch Latency

Patch latency is the time between a patch's release and your successful deployment of that patch. This is an indicator of a company's patching discipline and ability to react to exploits, "especially in widely distributed companies with many business units," according to Jaquith. As with basic coverage metrics, patch latency stats may show machines with lots of missing patches or machines with outdated patches, which might point to the need for centralized patch management or process improvements. At any rate, through accurate patch latency mapping, you can discover the proverbial low-hanging fruit by identifying the machines that might be the most vulnerable to attack.

How to get it: Run a patch management scan on all devices to discover which patches are missing from each machine. Cross-reference those missing patches with a patch clearinghouse service and obtain data on 1. the criticality of each missing patch and 2. when the patches were introduced, to determine how long each missing patch has been available.