Zh3r0 CTF 2020 - Digital Forensics

Isopach · June 18, 2020

There was so much guess… so much guess that I gave up and only did the Digital Forensics category and some of the other Forensics which were copied challenges from other CTFs.

MVP goes to the Google Source Code challenge, we found out AFTER the CTF that someone deleted the hints like phpinfo because it was an unrestricted sandbox, and occasionally someone would do an rm -rf so the whole website returned 403 Forbidden. Also according to the challenge creator, it is not guess.

Anyway, enough of that! I feel like I have learnt quite a bit about the Windows Registry and how to use the features of Autopsy from this CTF, so it was still a plus. Not sure if we will participate again next year though.

Digital Forensics


Category: Digital Forensics | 42 solves | 482 points

Challenge Description MR.Zh3r0 is a mathematician who loves what he does, he loves music and he is fairly good; like an average joe, with personal desktops but a really gullible person who could be phished or scammed easily! He had some bad colleagues in his office that led him to have some bad intentions towards them. One of his "HECKER" friend suggested to download some virus to destroy the data the other people has. As you would expect, this backfired. He has called the World's best forensics experts to come to his rescue! We were fortunately able to get his PC's image and some of the files in it. And We have a suspicion if he only downloaded one malware or more than one? And we need answers to some questions that follow, this would be your first assignment!
We found that his PC had some sort of problem with Time Zones even though he tries to reset it, it seems the malware is somehow able to edit the TimeZone to the malware author's name. How could a malware edit the TimeZone information if it had Administrator Privilege to the system!?

Note:- File for the challenges in this series is the same
Author : Amun-Ra
Flag format - zh3r0{authorname}

The challenge description mentions Timezones, and about how the Timezone is changed to the malware author name, which is the flag.

So we want to look for the TimeZone registry entry, typically found in HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\TimeZoneInformation.

Under the StandardName key, we see the value Cicada3310, which is the flag.


FLAG zh3r0{Cicida3310}

Good Ol’ IE

Category: Digital Forensics | 22 solves | 496 points

Challenge Description We haven't found the traces of how the virus could have got into the system. There are several attack vectors that a malware could get into the system which you will need to research upon. Now the question is, find the most probable way the malware(s) could've got in and the flag would be the name of the source.

Note:- File for the challenges in this series is the same
Author : Amun-Ra
Flag format - zh3r0{name of the malware source through which it entered the PC}
File - Same as the first challenge file

This one stumped me for a day. I actually gave up on it and then came back 2 hours before the CTF ended and suddenly had the inspiration to look at the URL list manually, one by one.

My keyword searcher grep’d a total of 27868 URLs, but they are grouped by location so the actual unique URL is actually much smaller - maybe around 1000 at most.

27k URLS

So I started from the bottom of the list and curl’d any suspicous URL I found - that is, stuff that are not microsoft or msn or other common software (eg. apache) links. The hint also says the victim is gullible, so we are looking for an interesting link.

I scrolled until I found hackinstagram.com, which unfortunately was a red herring. However, in the same registry file a few lines down, there was this link that did not exist http://w3.you-got-million-dollars-click-me.nr.hg.org.tech/ , or at least the HTTP ports were not accesible.

Good Ol' Flag

So I wrapped it in the CTF flag tags and it was the correct flag!

FLAG zh3r0{http://w3.you-got-million-dollars-click-me.nr.hg.org.tech/}


Category: Digital Forensics | 21 solves | 496 points

Challenge Description> Good job in finding the flag! We have found traces of yet another malware! The information we have is that MR.Zh3r0's music folder isn't really a music folder,(i.e), he's music folder seems to trigger the virus software somehow whenever he clicks it! Now he can't even open his default music folder to hear some good musics! We have a certain idea that somehow the virus might be redirecting the clicks to a different location where the virus resides or the location of music folder could be compltely different! You can find the flag at the right place when you look, it will be obvoius when u look at it!

Note:- File for the challenges in this series is the same
Author : Amun-Ra
Flag format - zh3r0{path to the malware file}

This was also pretty easy! The description basically says to find where the location of My Music is, so we go to the registry for Current User and look for where My Music points to.

I found the path by going to my own computer’s regedit and searching for My Music, which gave me the path HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Shell Folders and all I had to do was to find the same folder in the Image.E01.

Soundless Flag

FLAG zh3r0{C:\Users\zh3r0\Documents\Hades.exe}


Category: Digital Forensics | 18 solves | 497 points

Challenge Description Now, that you have found out how the malware got in, the next question is to find what the malware's name is, we have got a lead though, we found out that the virus wasn't removable from the system even after a restart. Although it hasn't been identified at a particular location, something is triggering it to restart as soon as he logs in! How could this happen? If you find the reason or the method for the above mentioned phenomenon you will find the flag there as an obvious one.

Note:- File for the challenges in this series is the same
Author : Amun-Ra
Flag format - zh3r0{malware name which will be at the right location you will need to find at}
File - Same as the first challenge file

The key takeaway from the description is “Finding a software that runs when system is restarted”.

So we go to the software registry in Windows\system32\config\ and under Microsoft\Windows\Current Version\Run\, in the execute key, there is the Malware name!

UnRemovable Flag

Wrap it in the flag tags and you’ve got the flag.

FLAG zh3r0{C:\windows\Program Files(x86)\Anubis.exe}

Run Forrest Run

Category: Digital Forensics | 16 solves | 498 points

Challenge Description Just like one other malware you found, we found traces of another malware which is able to start itself without user intervention, but this time we have no idea or info on when it starts or what triggers it, we only know that it runs automatically! If you have found out all the other flags then this one would be easy for you, this is a test of how much you know about forensics and where to look at properly!

Note:- File for the challenges in this series is the same
Author : Amun-Ra
Flag format - zh3r0{location of the malware file}
File - Same as the first challenge file

My teammate Kenneth chanced upon the flag randomly while searching for Anubis. Actually we submitted it to the earlier challenge but it was the wrong flag, but discovered it was meant for this!

I will find the intended solution and update the post soon.

Okay so basically I found this in 2 steps:

  1. Do keyword search for ‘Anubis.exe’ (include substring)

It returned 4 results, and only 1 of them was a registry file.

  1. Open the registry file and look one line up. There is the flag shown in the screenshot below.


FLAG zh3r0{zh3r0ctfmalware.exe}


Category: Digital Forensics | 16 solves | 10 points

Challenge Description I hope you liked this series! Hope you learned a lot from this from this!!! Thanks for the support as well!
Congratulations on solving this series!! You all did well and proved to be a good Digital Forensics Expert!
Have fun doing Forensics!

P.S. People who found the flag way before the wave 3 challs got released,... You are either a really Good Forensic expert or very lucky to stumble upon this!! Any ways congrats to you to for the fast solve!
Author : Amun-Ra
Flag - zh3r0{Digital_Forensics_Rocks!!!}

This is the bonus challenge for completing the category. As you can see, we are given a free flag which was the answer.

FLAG zh3r0{Digital_Forensics_Rocks!!!}



Category: Forensics | 126 solves | 325 points

Challenge Description I wonder if the snow loves the trees and fields, that it kisses them so gently?

Author : h4x5p4c3

We are given a file that cannot be unzipped on a Windows filesystem (I tried). Unzipping it on Mac messes up the filenames, so I did it on the latest Ubuntu 18.

After unzipping and doing cd snow, I realized it’s the exact same whitespace stego challenge as the one called snowflake in Nahamcon.

Thus, I present to you my one-line solution:

stegsnow -C -p $(cat .snowey/.../.../.secret.txt) chall.txt

This will return the flag. Thanks to the creator of stegsnow.

FLAG zh3r0{i5_it_sn0w1ng?}

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