Having your DNS server logs forwarded to a centralized location such as a log collector appliance or SIEM, or having full packet captures to an appliance (or both!) are two things that are essential in my mind for being able to effectively research events like these. Here are two suggested ways of doing this "on the cheap" (the only cost is hardware and time essentially) For the log collector/SIEM, an open source solution I can recommended is ELSA: enterprise-log-search-and-archive - Enterprise log search and archive (ELSA) is an industrial-strength solution for centralized log management. - Google Project Hosting "ELSA is a centralized syslog framework built on Syslog-NG, MySQL, and Sphinx full-text search. It provides a fully asynchronous web-based query interface that normalizes logs and makes searching billions of them for arbitrary strings as easy as searching the web. It also includes tools for assigning permissions for viewing the logs as well as email based alerts, scheduled queries, and graphing." For an open source full packet capture solution, I've read about openfpc: openfpc - Open Full Packet Capture - Google Project Hosting "OpenFPC is a set of scripts that combine to provide a lightweight full-packet network traffic recorder & buffering tool. It's design goal is to allow non-expert users to deploy a distributed network traffic recorder on COTS hardware while integrating into existing alert and log tools."
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