I recently posted the below on the SANS Internet Storm Center.
How do you detect what has changed in your environment? Is it possible to think beyond the alerts you get from your tools and consider what changes that you absolutely need to know about when they occur? When systems in your environment move from “normal” to “abnormal”, would you even notice?
Occasionally I have a credit card transaction denied. The most common reason for this is being in a part of the country that is outside my normal travel and spending patterns. When that happens, the panic quickly subsides and I recognize that something in my baseline has changed.
How can pattern and trend analysis apply in monitoring and defending your networks? Consider developing a similar baseline to detect possible unauthorized changes. This practice may very well help you detect changes that occur that do not follow the proper change control process and also give you deeper insight into the activities on your network. A practical step of creating a monthly calendar appointment named “What is missing from my baseline?” would help remind you to answer this question on an recurring basis. This will also help you develop a more meaningful relationship with your system administrators and application developers by asking them questions and learning more about these systems – both of which are highly encouraged.
To detect patterns and trends, consider developing a rolling 30, 60 or 90 day history in a few critical areas to show not only the current status, but also how they compare to recent activity over time. This insight will help identify patterns that exist beyond the point in time alerts that we regularly receive. Not every area requires this extended analysis, but in some cases showing a trend over time reveals pattens that would otherwise go unrecognized and unnoticed.
Consider the following for your baseline
Administrative logins after normal business hours
Administrative logins outside of approved change windows
Badge access to your building after normal business hours
Systems that restart outside of approved change windows
Services that restart outside approved change windows
Please use the comments area to share what’s in your baseline!
Russell Eubanks