Level 1 - Scratching the Surface

PreviousLevel 2 - Dee Na Saw as a need NextSPbCTF's Student CTF Quals

Last updated 3 years ago

Was this helpful?

Level 1 - Scratching the Surface

Scenario 1

Challenge 1

We've sent the following secret message on a secret channel.
Submit your flag in this format: TISC{decoded message in lower case}

We have a .wav audio file.

Open in Sonic Visualizer, and see that the channel 2 spectrogram looks like morse code.

Extract the second channel into a seperate out.r.wav file:

sox file1.wav out.r.wav remix 2

Decode the morse code:

The flag is TISC{csitislocatedinsciencepark}

Challenge 2

This is a generic picture. What is the modify time of this photograph?
Submit your flag in the following format: TISC{YYYY:MM:DD HH:MM:SS}

We can see this in the EXIF data.

The flag is TISC{2003:08:25 14:55:27}

Challenge 3

Nothing unusual about the Singapore logo right?
Submit your flag in the following format: TISC{ANSWER}

Binwalk shows us that there is a zip archive hidden in the file.

Extract it and we get a picture_with_text.jpg.

We can clearly see that before the JPEG magic bytes, there is some text.

This is a substitution cipher, the answer is

ANSWER TO THIS CHALLENGE IS HERE APPLECARROTPEAR

Scenario 2

Excellent! Now that you have show your capabilities, CSIT SOC team have given you an .OVA virtual image in investigating a snapshot of a machine that has been compromised by PALINDROME. What can you uncover from the image?
Once you download the VM, use this free flag TISC{Yes, I've got this.} to unlock challenge 4 - 10.
Check MD5 hash: c5b401cce9a07a37a6571ebe5d4c0a48
For guide on how to import the ova file into VirtualBox, please follow the VM importing guide attached.

Challenge 4

What is the name of the user?
Submit your flag in the format: TISC{name}.

The name is adam.

Challenge 5

Which time was the user's most recent logon? Convert it UTC before submitting.
Submit your flag in the UTC format: TISC{DD/MM/YYYY HH:MM:SS}.

Windows Security Logs log the Logon events (event ID 4624).

Note that the required time is in UTC, which is provided in the raw XML.

Challenge 6

A 7z archive was deleted, what is the value of the file CRC32 hash that is inside the 7z archive?
Submit your flag in this format: TISC{CRC32 hash in upper case}.

The command 7z l -slt archive.zip shows us extended info for the files in the archive, including the CRC32 hash.

We can see the CRC value in the output.

CRC = 040E23DA

Challenge 7

Question1: How many users have an RID of 1000 or above on the machine?
Question2: What is the account name for RID of 501?
Question3: What is the account name for RID of 503?
Submit your flag in this format: TISC{Answer1-Answer2-Answer3}. Use the same case for the Answers as you found them.

This information can be obtained using wmic useraccount get name,sid. The RID is the last part of the SID shown.

The flag is TISC{1-Guest-DefaultAccount}.

Challenge 8

Question1: How many times did the user visit https://www.csit.gov.sg/about-csit/who-we-are ?
Question2: How many times did the user visit https://www.facebook.com ?
Question3: How many times did the user visit https://www.live.com ?
Submit your flag in this format: TISC{ANSWER1-ANSWER2-ANSWER3}.

Edge has a History SQLite database that contains the web history.

The who-are-we page was visited twice. The other two websites were visited 0 times.

The flag is TISC{2-0-0}.

Challenge 9

A device with the drive letter “Z” was connected as a shared folder in VirtualBox. What was the label of the volume? Perhaps the registry can tell us the "connected" drive?
Submit your flag in this format: TISC{label of volume}.

We can find recently mounted devices in registry keys. The following registry key contains the mounted shared folder as a subkey:

Computer\HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\MountPoints2\

The name is vm-shared.

Challenge 10

A file with SHA1 0D97DBDBA2D35C37F434538E4DFAA06FCCC18A13 is in the VM… somewhere. What is the name of the file that is of interest?

I wrote a simple PowerShell script to find this.

Get-ChildItem -Path "C:\" -Recurse -Force |

ForEach-Object {
    if ((Get-FileHash -algorithm sha1 $_.FullName).Hash -eq "0D97DBDBA2D35C37F434538E4DFAA06FCCC18A13")
    {
        Write-Output $_.FullName
        break
    }
}