30 April, 2008

NoVASec: Memory Forensics

Richard Bejtlich arranged a NoVASec meeting on memory forensics for Thursday, April 24. Aaron Walters of Volatile Systems was the scheduled speaker. George Garner of GMG Systems, Inc., also showed up, so we were lucky enough to get two speakers for the price of one. (If you aren't aware, NoVASec is actually free). Aaron primarily talked about performing forensics and analysis on memory dumps, and afterwards Richard asked George to come up from the audience and talk about the challenges of actually acquiring the memory dumps.

Both Aaron and George were very knowledgeable and had a lot of interesting things to discuss. In fact, most of us didn't leave until after 22:00 so there was a good two and a half hours of technical discussion. It wouldn't do them justice for me to try and recap their talks, but I will mention a couple brief thoughts I jotted down while listening. If I'm getting anything wrong here, someone please pipe up and let me know.

First is that I saw some parallels between points mentioned by Aaron and Network Security Monitoring. Aaron stated that a live response on a system requires some trust of the system's operating system, is obtrusive, and is unverifiable. Dumping the RAM and performing an analysis using a trusted system helps mitigate these problems though I don't think he meant it solves them completely. Similarly, in NSM we use information that is gathered by our most trustworthy systems, network sensors that allow limited access, rather than trusting what we find on the host. In forensics and NSM, steps are taken to increase the trustworthiness and verifiability of information that is gathered.

Second, Aaron and George both seemed to agree that acquiring memory contents is not easy. Not only can it be difficult, but even a successful acquisition has issues. George pointed out that if you don't isolate the system, an attacker could be altering the system or memory as you acquire it. He also pointed out that dumping the memory is actually sampling, not an image, because the RAM contents are always changing even on a system that has been isolated from the network. One memory dump is just one sample of what resided in memory at a given time. More evidence and more sampling will increase the reliability of the evidence attained. Also, gathering evidence from multiple sources, for instance hard drive forensics, memory forensics and NSM, increases the probability evidence will be accurate and verifiable.

There was also some discussion of PCI and video devices as they relate to both exploiting systems and memory forensics. Acquiring memory can be an issue on systems using PAE since reading from the space used by PCI devices can crash the system. On the exploit side, the GPU and RAM on video cards can be used to help facilitate attacks, as can certain PCI devices. There is a lot of interesting work going on in this field, and George even mentioned that he has been working on tools for acquiring the contents of memory from video cards.

It was an excellent meeting.

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