Tag: HuntressCTF

Huntress CTF: Week 4 – Miscellaneous: MFAtigue

CTF, DFIR, Miscellaneous

MFAtigue

For any of these challenges where there’s a download and an online component, I’ll usually start with the files.

OK. So how can we get a password if we have access to the ntds.dit and the SYSTEM registry hive?

The iredteam.com article looks like a good place to start.

There’s a reference to dumping hashes using impacket.

I don’t have the SECURITY hive, but I do have the ntds.dit and the SYSTEM hive.

From here we’ll copy out all the hashes for user accounts. The accounts ending with $ are computer accounts so we won’t bother with those.

With the hashes isolated in a text file, we can run hashcat on the hashes using the rockyou wordlist.

…output continues…

We’ve got a match on the hash ending ..cadab42a.

Referencing that against our account information, we see that found hash is the password for JILLIAN_DOTSON.

Now for the url in the challenge. It brings us to a Microsoft sign-in page. We’ll use the account huntressctf\JILLIAN_DOTSON

And the cracked password of katlyn99…

Oh but wait. The account has MFA?!!

Hit the Send Push Notification

Then again,

And again…

After a mildly obnoxious number of repeated attempts….

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

Huntress CTF: Week 4 – Forensics: Bad Memory

CTF, DFIR, Forensics, Memory Analysis

Bad Memory

I spent a bit of time on this trying to get Volatility 2 to work with the Mimikatz plug-in. I was not successful. I was able to run the Volatility hashdump module.

I switched to Volatility3 and ran hashdump. For whatever reason the output of Volatility3 was different.

The only user besides the default accounts is for ‘Congo.’ Copy the hashed password and head over to https://hashes.com/en/decrypt/hash where we can search for the hash.

Yay, we got a match.

[Note: anecdotally I was advised that you could do this offline as well with Hashcat and the rockyou wordlist. I had tried that earlier but was using the Volatility2 output. 😦 ]

The last step is to convert ‘goldfish#’ to MD5.

Now just wrap it in the flag { } and you’re good to go.

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

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.