Potential PowerShell Obfuscation via Concatenated Dynamic Command Invocation

Last updated 22 days ago on 2026-02-09
Created a year ago on 2025-04-15

About

Detects PowerShell scripts that builds commands from concatenated string literals inside dynamic invocation constructs like &() or .(). Attackers use concatenated dynamic invocation to obscure execution intent, bypass keyword-based detections, and evade AMSI.
Tags
Domain: EndpointOS: WindowsUse Case: Threat DetectionTactic: Defense EvasionData Source: PowerShell LogsLanguage: esql
Severity
high
Risk Score
73
MITRE ATT&CK™

Defense Evasion (TA0005)(external, opens in a new tab or window)

Execution (TA0002)(external, opens in a new tab or window)

License
Elastic License v2(external, opens in a new tab or window)

Definition

Integration Pack
Prebuilt Security Detection Rules
Related Integrations

windows(external, opens in a new tab or window)

Query
text code block:
from logs-windows.powershell_operational* metadata _id, _version, _index | where event.code == "4104" and powershell.file.script_block_text like "*+*" // replace the patterns we are looking for with the 🔥 emoji to enable counting them // The emoji is used because it's unlikely to appear in scripts and has a consistent character length of 1 | eval Esql.script_block_tmp = replace( powershell.file.script_block_text, """[.&]\(\s*(['"][A-Za-z0-9.-]+['"]\s*\+\s*)+['"][A-Za-z0-9.-]+['"]\s*\)""", "🔥" ) // count how many patterns were detected by calculating the number of 🔥 characters inserted | eval Esql.script_block_pattern_count = length(Esql.script_block_tmp) - length(replace(Esql.script_block_tmp, "🔥", "")) // keep the fields relevant to the query, although this is not needed as the alert is populated using _id | keep Esql.script_block_pattern_count, Esql.script_block_tmp, powershell.file.*, file.path, powershell.sequence, powershell.total, _id, _version, _index, host.name, host.id, agent.id, user.id // Filter for scripts that match the pattern at least once | where Esql.script_block_pattern_count >= 1

Install detection rules in Elastic Security

Detect Potential PowerShell Obfuscation via Concatenated Dynamic Command Invocation in the Elastic Security detection engine by installing this rule into your Elastic Stack.

To setup this rule, check out the installation guide for Prebuilt Security Detection Rules(external, opens in a new tab or window).