OneDrive Pastejacking: The Sneaky Phishing and Downloader Campaign

ID

Data Source

Data Component

Detects

DS0017

Command

Command Execution

If proper execution policy is set, adversaries will likely be able to define their own execution policy if they obtain administrator or system access, either through the Registry or at the command line. This change in policy on a system may be a way to detect malicious use of PowerShell. If PowerShell is not used in an environment, then simply looking for PowerShell execution may detect malicious activity. It is also beneficial to turn on PowerShell logging to gain increased fidelity in what occurs during execution (which is applied to .NET invocations). [273] PowerShell 5.0 introduced enhanced logging capabilities, and some of those features have since been added to PowerShell 4.0. Earlier versions of PowerShell do not have many logging features.[274] An organization can gather PowerShell execution details in a data analytic platform to supplement it with other data.

PowerShell can be used over WinRM to remotely run commands on a host. When a remote PowerShell session starts, svchost.exe executes wsmprovhost.exe

For this to work, certain registry keys must be set, and the WinRM service must be enabled. The PowerShell command Enter-PSSession -ComputerName \<RemoteHost> creates a remote PowerShell session.

DS0011

Module

Module Load

Monitor for loading and/or execution of artifacts associated with PowerShell specific assemblies, such as System.Management.Automation.dll (especially to unusual process names/locations).[3][4]

Analytic 1 - Processes loading PowerShell assemblies

source="*WinEventLog:Microsoft-Windows-Sysmon/Operational" EventCode="7" | where ModulePath LIKE "%system.management.automation%" OR FileDescription LIKE "%system.management.automation%"

DS0009

Process

Process Creation

Monitor for newly executed processes that may abuse PowerShell commands and scripts for execution. PowerShell is a scripting environment included with Windows that is used by both attackers and administrators. Execution of PowerShell scripts in most Windows versions is opaque and not typically secured by antivirus which makes using PowerShell an easy way to circumvent security measures. This analytic detects execution of PowerShell scripts.

Powershell can be used to hide monitored command line execution such as:

net usesc start

Note: - The logic for Analytic 1 is based around detecting on non-interactive Powershell sessions (i.e., those not launched by a user through explorer.exe). This may lead to false positives when used in a production environment, so we recommend tuning any such analytics by including additional logic (e.g., looking for suspicious parent processes) that helps filter such events.- The logic for Analytic 2 is based around detecting on remote Powershell sessions. PowerShell can be used over WinRM to remotely run commands on a host. When a remote PowerShell session starts, svchost.exe executes wsmprovhost.exe.

Analytic 1 - Non-interactive Powershell Sessions

(source="WinEventLog:Microsoft-Windows-Sysmon/Operational" EventCode="1") OR (source="WinEventLog:Security" EventCode="4688") Image="powershell.exe" AND ParentImage!="explorer.exe"

Analytic 2 - Remote Powershell Sessions

(source="WinEventLog:Microsoft-Windows-Sysmon/Operational" EventCode="1") OR (source="WinEventLog:Security" EventCode="4688") Image="wsmprovhost.exe" AND ParentImage="svchost.exe"

Analytic 3 - Powershell Execution

(source="WinEventLog:Microsoft-Windows-Sysmon/Operational" EventCode="1") Image="C:\Windows\\powershell.exe" ParentImage!="C:\Windows\explorer.exe"|stats values(CommandLine) as "Command Lines" values(ParentImage) as "Parent Images" by ComputerName

Process Metadata

Consider monitoring for Windows event ID (EID) 400, which shows the version of PowerShell executing in the EngineVersion field (which may also be relevant to detecting a potential Downgrade Attack) as well as if PowerShell is running locally or remotely in the HostName field. Furthermore, EID 400 may indicate the start time and EID 403 indicates the end time of a PowerShell session.[275]

DS0012

Script

Script Execution

Monitor for any attempts to enable scripts running on a system would be considered suspicious. If scripts are not commonly used on a system, but enabled, scripts running out of cycle from patching or other administrator functions are suspicious. Scripts should be captured from the file system when possible to determine their actions and intent.

Analytic 1 - Script Block Logging Events

(source=WinEventLog:"Microsoft-Windows-PowerShell/Operational" EventID="4104" AND Image="powershell.exe" AND (CommandLine="-enc" OR CommandLine="-ep bypass" OR CommandLine="-noni*")