The Network Capture Playbook Part 1 – Ethernet Basics

Capturing network packets is the first step in any kind of network analysis or network forensics situation. Few people ever consider this an important step, but this is really where the analysis result can be heavily distorted if you’re not careful. During Sharkfest 2016 I talked about how important the capture process and it’s preparations are, and decided to start a series of blog posts about how to do network packet captures. So here we go with the first one, starting with basic network capturing in a wired environment.

My packet analysis toolset

As any analyst (regardless of the topic being networks, IT security, forensics etc.) will tell you, it’s almost always a combination of tools that is used to get the results. And since I thought it might be useful, here’s my list of what I primarily use when analyzing packets.

Sharkfest 2016 recap

Another Sharkfest has come and gone, and once again it has been a great conference. If you’re into packet analysis, network forensics or network troubleshooting there is no other event that has the same density of information. It’s really a “specialist” conference, in a very open and friendly way, and newcomers are always welcome.

Megalodon challenge solution

During Sharkfest 2015 I put up a challenge that was different from the usual challenges offered. The pcap files are a lot bigger, the task to solve less specific, and the answer not a simple “easy to verify” answer. I promised to put up my solution a few months after posting the challenge to this blog, but then some things got in the way. And then… some more got in the way. Sorry for that, but sometimes it can’t be helped.

Verifying IoCs with Snort and TraceWrangler

After detecting a network breach it is a good idea to scan the network for further Indicators of Compromise (IoC) to check for further malicious activity. The IoCs are usually derived from forensic investigations into network packets and compromised hosts, and can be quite unique when it comes to more sophisticated attacks (let’s avoid mentioning the APT buzzword here… oh, wait… darn!).

Frame bytes vs. frame file headers

When capturing frames from a network there is more information recorded into the capture file than just the bytes of each frame. If you have ever looked at the PCAP or PCAPng file format specifications you have seen that each frame has an additional frame header containing important information that wasn’t part of the frame itself.

The Megalodon Challenge

This year at Sharkfest I offered a special capture file challenge I called “The Megalodon Challenge”. Other than the “normal” challenges you could find at The Reef it was not limited to the size of 100MB, and the solution cannot be reduced to a couple of words or numbers. After Sharkfest I was asked if I could put up the challenge so that people that haven’t been at the conference (or didn’t know about the challenge) could give it a shot. So here it is.

Sharkfest 2015 recap

“Jasper, do you have a minute?”

I think that is the one sentence that I heard most at Sharkfest 2015, which is the annual Wireshark developer and user conference. Which makes it the most interesting place to be for anyone doing network analysis, for business or fun/hobby (yes, those exist). People asking me for a minute involved Wireshark core developers, other speakers, and of course Sharkfest attendees.