Threat Level: green Handler on Duty: Tom Webb

SANS ISC: SEC505 DFIR capture script: snapshot.ps1 - Internet Security | DShield SANS ISC InfoSec Forums

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SEC505 DFIR capture script: snapshot.ps1

I just spent a fair bit of time preparing to take the GIAC Security Expert exam as part of the requirement to recertify every four years. I first took the exam in 2012, and I will tell you, for me, one third of the curriculum is a "use it or lose it" scenario. The GSE exam covers GSEC, GCIH, and GCIA. As my daily duties have migrated over the years from analyst to leadership, I had to "relearn" my packet analysis fu. Thank goodness for the Packetrix VM and the SANS 503 exercises workbook, offsets, flags, and fragments, oh my! All went well, mission accomplished, I'm renewed through October 2020 and still GSE #52, but spending weeks with my nose in the 18 course books reminded of some of the great tools described therein. As a result, this is the first of a series on some of those tools, their value, and use case scenarios.

I'll begin with snapshot.ps1. It's actually part of the download package for SEC505: Securing Windows and PowerShell Automation, but is discussed as part of the GCIH curriculum. In essence, snapshot.ps1 represents one script to encapsulate activities specific to the SANS Intrusion Discovery Cheat Sheet for Windows.

The script comes courtesy of Jason Fossen, the SEC505 author, and can be found in the Day 5-IPSec folder of the course download package. The script "dumps a vast amount of configuration data for the sake of auditing and forensics analysis" and allows you to "compare snapshot files created at different times to extract differences."

To use snapshot.ps1 place the script into a directory where it is safe to create a subdirectory as the script creates such a directory named named for the computer, then writes a variety of files containing system configuration data.  Run snapshot.ps1 with administrative privileges.

The script runs on Windows 7, Server 2008, and newer Windows operating systems (I ran it on Windows 10 Redstone 2) and requires PowerShell 3.0 or later. You also need to have autorunsc.exe and sha256deep.exe in your PATH if you want to dump what programs are configured to startup automatically when your system boots and you login, as well as run SHA256 file hashes. That said, if you must make the script run faster, and I mean A LOT FASTER, leave file hashing disabled at the end of the snapshot.ps1 for a 90% reduction in run time. However, Jason points out that this is one of the most useful aspects of the script for identifying adversarial activity. He also points out that snapshot.ps1 is a starter script; you can and should add more commands. As an example, referring back to toolsmith #112: Red vs Blue - PowerSploit vs PowerForensics, after importing PowerForensics, you could add something like Get-ForensicTimeline | Sort-Object -Property Date | Where-Object { $_.Date -ge "12/30/2015" -and $_.Date -le "01/04/2016" } | WriteOut -FileName Timeline which would give you a file system timeline between the 12/30/2015 and 01/04/2016.But wait, there's more! Want to get autoruns without needing autorunsc.exe?  Download @p0w3rsh3ll's AutoRuns module, run Import-Module AutoRuns.psm1, then Get-Command -Module AutoRuns to be sure the module is on board, and finally comment out autorunsc.exe -accepteula -a -c | Out-File -FilePath AutoRuns.csv then add Get-PSAutorun | WriteOut -FileName AutoRuns.

It's then as simple as running .\Snapshot.ps1 and watch your computer-named directory populate, 0V3RW4TCH-2016-10-31-9-7 in my case, per Figure 1.

Figure 1: Snapshot.ps1 run

Most result files are written in machine-readable XML, CSV, and TXT, as well as REG files generated by the registry exports via reg.exe.

A great example of a results file, is spawned via dir -Path c:\ -Hidden -Recurse -ErrorAction SilentlyContinue | Select-Object FullName,Length,Mode,CreationTime,LastAccessTime,LastWriteTime | Export-Csv -Path FileSystem-Hidden-Files.csv. The resulting CSV is like a journey down evil memory lane, where all the nuggets I've tested in the past leave artifacts. This would be EXACTLY what you would be looking for under real response scenarios, as seen in Figure 2.

Figure 2: Snapshot.ps1 grabs hidden files

Sure, there are bunches of related DFIR collection scripts, but I really like this one, and plan to tweak it further. Good work from Jason, and just one of many reasons to consider taking SEC505, or pursuing your GSE!

Russ McRee

156 Posts
ISC Handler
You should also check out the Kansa framework


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