Threat Level: green Handler on Duty: Didier Stevens

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File2pcap - A new tool for your toolkit!

One of our readers, Gebhard, submitted a pointer to a tool today, released by Talos, that I wasn't familiar with.  However, when I realized it could generate packets, I had to try it out.  Its called File2pcap.  The concept of the tool is that instead of having to download a file and capture the traffic in order to write detection content, the tool would simulate the download and generate the traffic that you would see.  You get a nice pcap in the end.  I took a relatively benign phishing pdf (it had a link in it) and used it for my test.  The tool doesn't have any documentation until you compile it and run it.  Here are your options:


I ran a few test scenarios with it.  One for HTTP and one for SMTP.  For the HTTP, I used the following command line and specified a file name:

./file2pcap -mh -p 45678:8443 Wire_transfer_Notification.pdf -o httpout.pcap
It shows you if its working verses just returning a command prompt:
"Writing to httpout.pcap"
You can see by the packets, it matches the ports I told it to use:
Here is what it looks like when you follow the TCP stream:
For the SMTP I ran the following command:
./file2pcap -ms Wire_transfer_Notification.pdf -o smptout.pcap
Here is the data from following the TCP stream:

I played with several of the options.  You can also run more than one protocol in a single command line (you can't specify a file name running multiple modes, it will generate them for you):
./file2pcap -msh Wire_transfer_Notification.pdf
Writing to Wire_transfer_Notification.pdf-smtp.pcap
Writing to Wire_transfer_Notification.pdf-http-get.pcap
This is a very handy tool to have when you need to generate packets quickly to write content for file transfer detection.  Its definately one I'll add to my toolkit!



165 Posts
ISC Handler
May 26th 2017

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