#Filtering out all the Event Records associated with the ScriptBlockID into a single PS Object To create a single PowerShell object containing all the artifacts found with this process, open PowerShell ISE, replace the location of the offline EVTX (in our example, Operational.evtx) and ScriptBlock ID (in our example, 51baf005-40a5-4878-ab90-5ecc51cab9af), and execute the following to create a single PowerShell object as shown in the example below. The ScriptBlock ID for this fragment, 51baf005-40a5-4878-ab90-5ecc51cab9af, appears on the right in Figure 2.įigure 2: Detail showing ScriptBlock ID for fragment 9 7 The content o f one of these artifacts, contained in the C:\Windows\System32\winevt\Logs\Microsoft-Windows-PowerShell%4Operational.evtx event log, is shown in the lower portion of the Event Viewer screen in Figure 1.įigure 1: 4104 events in the Operational.evtx log Filtering for event ID 4104 returns a list of those artifacts. W hen a large PowerShell script runs, it results in a number of fragmented artifacts deposited across multiple logs. However, the ability to extract or reconstruct (partially or in full) a very large PowerShell script from multiple event records is still lacking in most of the tools available. In a recent post, we took a step-by-step look at decoding malicious PowerShell activity in a specific incident, using such tools. The open-source community has a variety of effective tools to use when parsing or automatically hunting for suspicious events. If a script is very large, PowerShell breaks it into multiple parts before logging those under Event ID 4104, which will be the focus of this article. This feature records commands and entire scripts in event logs as they execute. With the release of PowerShell 5.0 back in 2015, Script Block Logging was enabled by default. In a previous post, we explained various forensic artifacts left behind by PowerShell. This poses a problem for defenders and researchers alike. It is easy to understand its popularity among attackers: Not only is it present on all versions of Windows by default (and crucial to so many Windows applications that few choose to disable it), this powerful interactive CLI and scripting environment can execute code in-memory without malware ever touching the disk. Adversaries continue to abuse PowerShell to execute malicious commands and scripts.
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