/* CAT(1) */

By Jeff White (karttoon)

*EDIT - 27AUG2018*
I converted this to a dedicated Cuckoo module and it far exceeds the capabilities here. Branch can be found here for Cuckoo and general code on GitHub here.

In this post I want to give a brief introduction to a new tool I'm working on called "Curtain". It will be complimentary to another post I'm working on for $dayjob where I created a Curtain Cuckoo module.

Curtain is basically just a small script that can be used to detonate malicious files or PowerShell scripts and then scrape out the ScriptBlock logs for fast analysis. I'll go into the concept behind it more in my other post.

The idea here then is to get that same functionality but without Cuckoo, as it's not always available to everyone or people may not want to much with installing custom modules, and I wanted something standalone.

That being said, there are still a few requirements for this alternate iteration which, admittedly, was my first version before I decided to try and streamline it more for work usage.

The usage of the script is fairly straight forward and you simply pass it either a PS1 script OR a file which it will try to execute and then report back the ScriptBlock event logs. For PS1 scripts, it will launch PowerShell, otherwise it will rely natively on the extension and the OS the recognize/execute it. It'll wait 10 seconds and then simply scrape the logs, parse them into a simple HTML file, and display it on the host.

Below is a simple example of the script in action...

$ ./curtain.sh test.ps1 [+] Reverting to snapshot - curtain [+] Starting headless VM 2017-11-09T10:51:39.463| ServiceImpl_Opener: PID 26072 [+] Copying curtain.ps1 to virtual Guest [+] Sending target file to detonate [+] Launching Curtain PS script for - test.ps1 [!] Sleeping for 10 seconds to let malware doing its thang... [+] Transferring output from script [+] Grabbing a screenshot of the desktop [+] Killing virtual Guest [+] Launching site...

If you click HERE you can see the resulting output that gets created.

Nothing too crazy or fancy but it allows you to see how things flowed and have some visibility into the deobfuscated PowerShell which was executed on the Guest machine. I haven't yet beautified it so it's pretty raw at the moment but figured I'd put it out there if there was a need for it.

The GIT for this script is up and you'll need to fill out a few variables in the "curtain.sh" script to make it work.

Hopefully this helps if you do not have Cuckoo available or just want a quick way to be able to parse out PowerShell execution activity from a code sample.

There is also a file "psorder.py" I've included in the GIT repo. At some point I was writing a manual PowerShell deobfuscator and, while that is a fruitless endeavor, there are some benefits using it in tandem with Curtain for token replacement/etc.

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