3. RC6

For this challenge, I unable to decrypt shellcode with script, however my approach is more towards malware behavior analysis as it check for the username z0mb13 and runs procmon and check what is the shellcode’s behaviour with EnumDesktopA

rc6-1.png

To solve it create another user profile with the name z0mb13

rc6-2.png

Set up capture file for process name with crypt.exe

rc6-5.png

GetUserName invoked:

rc6-3.png

rc6-6.png

And before crypt.exe closed, here are the processes:

rc6-4.png

There is a noticeable repetitive string in the search path with echo 525753437b6e305f7734595f7930755f643363727970375f376831357d.exe

Decode the hex string with give us the flag:

rc6-7.png

Flag: RWSC{n0_w4Y_y0u_d3cryp7_7h15}

Reference: https://cocomelonc.github.io/tutorial/2022/06/27/malware-injection-20.html