![]() Once our tool cannot be detected at a glance, we have several possible options for session exfiltration. A simple way would be by entering the command in the ~/.bashrc file, so every time Johnny executes Bash, asciinema will be storing the whole session. ![]() Next, we must think about how we can integrate the session log without the user noticing. We also find that the screen output of the URL must be deleted in the upload file: asciinema/commands/upload.py.Īfter those changes, we already have our asciinema without a trace:Īt this point, we must upload our tool fork to a github that does not attract too much attention. With a simple grep on the asciinema path, we find that these messages are stored in the asciinema/commands/record.py file, so we are going to delete them. Very valuable information that can be used in a malicious way.īelow, we will see if we could use it as a Linux keylogger and what modifications would be necessary to apply.įirst of all, we observe how the session logging functionality works.Īs you can see, we have some info messages that should be deleted, as well as the URL where the sample has been uploaded.īeyond this information, it does not seem to modify the user’s environment, so we keep going in search of the source code files that store the information messages. Thus, in the following article the analysis of the asciinema tool will be carried out, as well as the different possibilities of use and how it can be integrated with an attack vector.Īsciinema is a very nice tool that I usually use for demos whose sole function is to register the user’s session and to provide a URL that allows us to easily share the user’s activity. However, there are other simpler (and equally effective) methods to carry out the exfiltration of information, such as through tools that were not initially designed for this purpose and which, with relatively simple adjustments, allow us to carry it out. In the preparation of our audits, we often waste a lot of time developing tools that require a lot of work and, in many cases, do not go unnoticed by those users with a more technical profile.
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