Investigation - InCTF Internationals 2020

Full solution of Investigation challenge from InCTFi 2020.

tl;dr

  • Extract process last run time from the windows registry.
  • Extract process run count from the windows registry.

Challenge points: 100

No. of solves: 117

Challenge Author: stuxn3t

Challenge description

Description

You can download the file from here: Google Drive.

Initial analysis

We are provided with a Windows memory dump. I’ll be using Volatility to analyze, extract relevant artefacts.

Finding the profile

We shall use the imageinfo plugin to find the profile of the memory dump

$ volatility -f windows.vmem imageinfo

imageinfo

So let us use the profile as Win7SP1x64.

Answering 1st question

Question 1: When did Adam last use the Windows calculator?

So to find out when the calculator was last run, let us first try pslist, because if calc.exe was running in the system, then we can easily get the time stamp directly from the output generated by the pslist plugin.

$ volatility -f windows.vmem --profile=Win7SP1x64 pslist

pslist

Well, we do not find any trace of calc.exe being executed. However, we do have a different source to obtain all the evidence we need. That is the Windows Registry.

The windows registry is a very very rich source of information. It has so many details that a forensic examiner needs to extract its information.

The details of processes like run count, Last run time, execution path etc… can be found in the Windows registry. To list out the registry hives, we can use the hivelist plugin.

$ volatility -f windows.vmem --profile=Win7SP1x64 hivelist

hivelist

The important hive for this challenge is the NTUSER.DAT. So let me dump the hive and proceed to analyze its contents.

$ volatility -f windows.vmem --profile=Win7SP1x64 dumpregistry -o 0xfffff8a00256d010 -D . 

dumpregistry

I will be using Eric Zimmerman’s Registry Explorer to load and analyze the registry.

PATH: Software\Microsoft\Windows\CurrentVersion\Explorer\UserAssist{CEBFF5CD-ACE2-4F4F-9178-9926F41749EA}\Count

ezregexp

As highlighted, the last run time of calc.exe is 2020-07-21 18:21:35. Converting that to the format mentioned in the description would result in 21-07-2020_18:21:35.

Answering 2nd question

In the same registry, we can also find the number of time Google Chrome was executed on the system.

chrome

As highlighted, the number is 19.

Flag

Let us concatenate the two answers as mentioned.

FLAG: inctf{21-07-2020_18:21:35_19}

For further queries, please DM me on Twitter: https://twitter.com/_abhiramkumar

References