Forensic

Challenge
Link

Portugal (100 pts)

Sussy (100 pts)

saveme (100 pts)

Sharing is Not Caring (257 pts)

Snooz (436 pts)

Portugal (100 pts)

Description

I accidentally left my computer unlocked at the coffee shop while I stepped away. I'm sure that someone took advantage of the opportunity and was searching for something.

Author : d33znu75

Solution

Given memory dump, analyze the running process using volatility.

python .\vol.py -f .\ctf\akasec\portugal\memdump1.mem windows.pslist

From the description we know that someone was searching for something and we can see on the running process there are chrome process. Chrome store the history on history file, so lets take a look on list file on the memory.

So there is history chrome file at 0x81595680, lets dump the history file.

We can't directly open the database using sqlite3 because it's not valid sqlite3 (maybe some trailer error). But we still can see the content of the database by utilizing strings command.

There are some suspicious strings

Integer before the string actually the index of the string, so we need to sort the pairs of index and value then combine it.

Flag: AKASEC{V0L4T1L1TY_f0r_chr0m3_s34rch_h1st0ry}

Sussy (100 pts)

Description

Something Fishy's Going on in Our Network

Author : d33znu75

Solution

Given pcap file, open it using wireshark. The first packet looks suspicious.

If we decode the domain we will get value below

Looks like 7z header, so lets do scripting to dump the the 7z file from the subdomain. Convert the pcapng to pcap file.

7z file protected with password, crack it using john with rockyou as wordlist. Got the password hellokitty then get pdf file named flag. It also protected with password, crack it using john again. Got the password meow.

Open the pdf file and got the flag

Flag: AKASEC{PC4P_DNS_3xf1ltr4t10n_D0n3!!}

saveme (100 pts)

Description

You know what to do. Get after it!

WARNING:"It's a malware, BE CAREFUL"

Author: samaqlo

Solution

Given docm file, look on the macro with olevba and oleid.

Looks like there is no embedded macro on the docm file. Lets try to unzip the file.

at word/document.xml there are suspicious values which are consist of hex strings. We can also validate it through opening the docm and there are some text in white color. The first 2 bytes looks like a valid PE signature.

Lets dump the whole PE file.

Open the PE file using IDA.

Looks like it obfuscated, lets try to upload it on virustotalarrow-up-right. There is suspicious URL contacted by the executable.

dump.exe should be the dropper and it will download ransomware.exe. Download ransomware.exe then open it using dnSpy because it is .net executable.

From the higlighted line we know the key, iv, and algorithm. Write script to automate decryption process of the encrypted file.

Open the images (144).png and got the flag

Flag: AKASEC{F_MiCRoSft_777}

Sharing is Not Caring (257 pts)

Description

My friends and I use the same computer on campus and have a shared folder to exchange files. After submitting the flag for the challenge, it was leaked, and someone obtained it without my knowledge. I'm unsure how they got it.

Author : d33znu75

Solution

Given file ad1 and pcap. Open the pcap file using wireshark. There are several http traffic and there is suspicious URL which is freerambooster.000webhostapp.com.

Access the URL and click download button

Open FREE_RAM.exe using dnSpy or ILSpy.

Looks like the executable run several powershell command, lets take a look on powershell history. Open ad01 file using ftk imager then go to .

So there is sslkey.log stored at SIGNUP directory, it will be very useful because it will let us decrypt the SSL traffic. There is no sslkey.log in SIGNUP directory but there is sslkey.log in SIGNUP\ink directory.

Load the sslkey.log file by clicking preferences > Protocols > TLS > (Pre)-Master-Secret log filename. After that look at HTTP2 traffic and there will be request to URL that contains flag.

Flag: AKASEC{B4s1c_M4lw4r3_4nd_PC4P_4n4lys1s}

Snooz (436 pts)

Description

don't wake me up, I want a snooze u will find everything on my laptop!!

https://we.tl/t-66EoXGwbVQarrow-up-right

Author: samaqlo

Solution

Given memory dump and pcap file. Open pcap file using wireshark. There are several HTTP traffic and there is suspicious HTTP request which is /download.dat.

Decode the string and write to file.

Open the executable using dnSpy.

So the original executable name should be snooz.exe. Lets check available process on memory dump.

We can see on image above that there is snooz.exe with PID 3200. Dump the executable using command below

Open file.0xa38425992e50.0xa384269f2150.ImageSectionObject.snooz.exe.img using dnSpy. Look at class a.

  • So it use AES as the encryption algorithm with mode ECB. For the key the value is from the second argument.

Through analyze feature we can see which line of code that call the a.b function.

So the key is <Module>.c(num6, num7, num8), lets take a look on <Module>.c

  • Basically it just do xor with data in resource named "resource". A_2 is static value and the size of each value in array is 1 byte. So in this case we can just search the value for A_2 then iterate on all data in "resource".

So there is two possible value for num8, (Type.EmptyTypes.Length + -1963321438) or (Type.EmptyTypes.Length + 182). Type.EmptyTypes.Length is 0 (we can validate it through running the code). So the possibility is negative value or 182. 182 looks like legit value because it is 1 byte so lets try to iterate the resource using 182 as A_2.

There is suspicious string that looks like a key which is at index 315. On function a.a we can see that the executable listen at port 1337. So lets open the pcap again and filter for port 1337.

"pastecode" mentioned on the text and there is password also "5n00zm3m3rbr0z". Because i can't find the pastecode link i tried to do simple grep string on the memory dump.

Decode the base64 value then write it to file.

At first i tried to do bruteforce but i can't find valid password. So i chose to dump the strings on memory then find some string related to "password".

On dumpl i found interesting string related to password.

Use "Samaqlo@Akasex777" as the password and got flag.jpg.

Looks like flag.jpg doesnt show flag, lets try to do some stegano stuff.

Flag: AKASEC{05-10-2023_free_palestine}

Last updated