LetsDefend Challenge: Memory Analysis (Walkthrough)

Analysing Memory Dump extracted from a compromised Windows Host

Scenario

A Windows Endpoint was recently compromised. Thanks to our cutting-edge EDR/IDS solution we immediately noticed it. The alert was escalated to Tier 2 (Incident Responders) for further investigation. As the Forensics guy, I was given the memory dump of the compromised host. I would continue to investigate.

Analysis

1. What was the date and time when Memory from the compromised endpoint was acquired?

I used the windows.info plugin, which pulls high-level metadata about the memory image itself -things like the OS version/build, kernel base address, number of processors, and, most importantly for this question, the system's boot time and the time the sample was collected. This is usually the first plugin to run against any new memory dump, since it confirms the image is readable and gives useful context (OS build, architecture) before running any other plugin.

vol -f dump.mem windows.info

2. What was the suspicious process running on the system?

To identify malicious processes more systematically, I kept the following checklist in mind:

• Suspicious or randomly-named processes
• Suspicious parent-child relationships (example: winword.exe spawning powershell.exe)
• Broken parent relationships (a process whose parent doesn’t match its known-legitimate parent)
• Advanced evasion methods: process injection, DLL injection, process hollowing

vol -f dump.mem windows.pslist

Running this, I spotted a rogue lsass.exe whose parent process was explorer.exe instead of wininit.exe, which is the only legitimate parent lsass.exe should ever have. This broken parent-child relationship was the giveaway that this particular lsass.exe was masquerading as the legitimate Windows credential process.

Rogue lsass.exe

3. Analyze and find the malicious tool running on the system by the attacker

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I dumped the malicious process to disk so it could be analyzed as a standalone file, and then calculated its MD5 hash to use as a unique identifier for lookups.

vol -f dump.mem windows.pslist --dump --pid 7592

I checked the hash against Hybrid Analysis first, but it didn’t return anything conclusive. Submitting the same hash to VirusTotal, however, returned a clear detection and identified the name of the tool, as shown below.

Submitted the dumped file hash to Virustotal

4. Which User Account was compromised?

Here I used the envars plugin, which lists the environment variables associated with each process at the time of acquisition. Since environment variables like USERNAME and USERDOMAIN are set per-session for the user context a process is running under, this is a quick way to tie a suspicious process back to the specific account it was executed as, without having to cross-reference session/logon tables separately.

vol -f dump.mem windows.envars

5. What is the compromised user password?

I first dumped the credential hashes stored in memory:

vol -f dump.mem windows.hashdump

I then took the NTLM hash for the compromised account, saved it into a text file, and cracked it offline using hashcat. The lab environment didn’t have a wordlist directory available locally, so I cloned a repo containing rockyou.txt and used it as the dictionary for the crack:

hashcat -m 1000 ntlm.txt /root/Desktop/ChallengeFile/rockyou.txt --force

Cracking NTLM Hash with Hashcat

Thanks for reading!! If you are the visual learner type, I got the video walkthrough here: https://youtu.be/Cb9ZmcVL12M?si=1ZxmHOW38PAzUXCa

Peace.