Huntress CTF: Week 3 – Miscellaneous: Who Is Real?, Operation Eradication

CTF, DFIR, Miscellaneous

Who Is Real?

This was a change of pace from what a lot of the CTF has been; lots of malware and deobfuscation. In this challenge we’re tasked with figuring out which faces are real and which have been AI generated.

Before starting the challenge, I familiarized myself with

https://whichfaceisreal.com/learn.html

It gave me good ideas of things to look for regarding teeth, glasses, earrings, other faces in photos, etc.

Eventually, I was able to get 5 right in a row.

Operation Eradication

Let’s take a look at the configuration file.

This looks like a config file for rclone.

Using this information, and the url provided from the challenge, we can update our rclone config file.

Now using rclone we can connect to the remote location and hopefully start deleting these ‘sensitive’ files. If only it were so easy.

I was able to get a directory listing, so I knew that my credentials were successfully connecting.

I was all over the command options at https://rclone.org. Every DELETE or SYNC operation I could think of was failing.

At my wit’s end I pinged a friend who suggested trying to overwrite the files with a 0 bit file. If successful the files would still be there, but the content gone – so essentially, they’d be safe again.

Using the file listing from the server, I wrote a PowerShell script that would touch, or create a 0 byte file, locally for each file names.

Next the script would run the rclone copy command to copy the local 0 byte files to the network location.

I run the PowerShell script and then return to the webpage and refresh…

DOH! There was a typo in one line of the script. I’ll re-run the file listing command again. All but one file have the 0 byte file size.

Run the copy command one more time to take care of our errant file and…

Success!

Use the tag #HuntressCTF on BakerStreetForensics.com to see all related posts and solutions for the 2023 Huntress CTF.

Huntress CTF: Week 3 – Forensics: Rogue Inbox, Texas Chainsaw Massacre: Tokyo Drift

CTF, DFIR, Forensics

Rogue Inbox

Originally I was looking at this in Timeline Explorer, but decided to switch to Excel.

Swimming and scanning through a sea of log entries, an anomaly showed itself.

For this one I just copied the values out by hand.

Huntress CTF: Week 3 – Forensics: Rogue Inbox, Texas Chainsaw Massacre: Tokyo Drift

The download is Application Logs.evtx

If you open the log with Event Viewer, you may see there’s an entry for a (non-actual) event ID of 1337.

The error content isn’t very helpful.

Let’s take a hint from the title and run the event log through Chainsaw.

Nothing significant when using the stock rules. What if we poke specifically at Event ID 1337.

That looks interesting.

Copy the binary data and bring it over to CyberChef

From unintelligible binary to unintelligible PowerShell.

Copy the output and save it is a .ps1 file. We can run the script through PowerDecode.

PowerCode works down through the obfuscation layers, finally revealing the plain text of the command.

Now that the code has been deobfuscated, time to figure out what it does. I copied the code into PowerShell ISE and start isolating the different command sections.

One of the commands does a DNS lookup and directs the output into a string.

If we run the command on its own we can see the output. The last part of the script checks to see if the output matches the pattern of a Base64 encoded string, and if so, decodes it.

Now what was that about Tokyo?

Use the tag #HuntressCTF on BakerStreetForensics.com to see all related posts and solutions for the 2023 Huntress CTF.

Huntress CTF: Week 3 – M Three Sixty Five

CTF, DFIR, M365

This is a multipart challenge. All the flags can be found within the live Microsoft 365 instance that we’ll ssh into.

The clue is street address. I’m not too fluent in the capabilities of AADInternals, so the first thing I do is head over to the documentation.

If I do a search on ‘street’ I see that it’s part of an Output example for Get-AADintTenantDetails

Ok, let’s give that command a go.

And there’s the flag under the street value.

For the next one, It not so subtly says that Conditional Access Policies will be part of this, so again we reference the docs. Get-AADIntConditionalAccessPolicies seems like a good candidate.

Two for two.

Microsoft Teams will be our focus on the third one. There’s dozens of Teams commands available within AADInternals. If we focus on message, that will get us to Get-AADIntTeamsMessages.

Having the documentation for the syntax really helped on this one.

And for the last one, no there isn’t a Get-AADIntPresident command. That would be too easy. How about a command that will show us all the users?

Scrolling up through the output, we find that the President (PattiF), has a flag in the telephone number field.

4 out of 4.

Use the tag #HuntressCTF on BakerStreetForensics.com to see all related posts and solutions for the 2023 Huntress CTF.

Huntress CTF: Week 2 – Miscellaneous: Rock, Paper, Psychic

CTF, DFIR, Miscellaneous

Rock, Paper, Psychic

Do you want to play a game?

You can see the basic flow of the game above. You put in your choice, then after some calculation the game chooses, and what do you know – the game always makes the winning choice.

How about a nice game of Chess?

Having played the game a couple times to get familiar with the flow, I ran the program using x64dbg.

Hit F9 a few times until it the program gets to your input choice.

Once you’ve typed in your selection in the command window, back to x64dbg. From here we will step over (F8) the instructions 1 by one.

Continue to hit F8, observing as the rest of the game text appears.

Global Thermonuclear War

In x64dbg, we see that the program tests 2 values and then does a JNE (Jump if not Equal) command to another function 416C6A.

If we use the debugger and change this to JE (Jump if equal to):

Who you calling cheater?

Use the tag #HuntressCTF on BakerStreetForensics.com to see all related posts and solutions for the 2023 Huntress CTF.