[New Rule] PowerShell Reflection Assembly Load (#1559)

* Create defense_evasion_posh_assembly_load.toml * Update defense_evasion_posh_assembly_load.toml * Update rules/windows/defense_evasion_posh_assembly_load.toml Co-authored-by: Samirbous <64742097+Samirbous@users.noreply.github.com> * Change event.code to event.category * Update rules/windows/defense_evasion_posh_assembly_load.toml Co-authored-by: Justin Ibarra <brokensound77@users.noreply.github.com> Co-authored-by: Samirbous <64742097+Samirbous@users.noreply.github.com> Co-authored-by: Justin Ibarra <brokensound77@users.noreply.github.com>
2021-12-08 17:59:17 -03:00
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+[metadata]
+creation_date = "2021/10/15"
+maturity = "production"
+updated_date = "2021/10/15"
+
+[rule]
+author = ["Elastic"]
+description = """
+This rule detects the use of Reflection.Assembly to load PEs and DLLs in memory in Powershell Scripts. Attackers use
+this method to load executables and DLLs without writing to the disk, bypassing security solutions.
+"""
+from = "now-9m"
+index = ["winlogbeat-*", "logs-windows.*"]
+language = "kuery"
+license = "Elastic License v2"
+name = "Suspicious .NET Reflection via PowerShell"
+references = [
+    "https://docs.microsoft.com/en-us/dotnet/api/system.reflection.assembly.load",
+]
+risk_score = 73
+rule_id = "e26f042e-c590-4e82-8e05-41e81bd822ad"
+severity = "high"
+tags = ["Elastic", "Host", "Windows", "Threat Detection", "Defense Evasion"]
+timestamp_override = "event.ingested"
+type = "query"
+
+query = '''
+event.category:process and 
+  powershell.file.script_block_text : (
+    "[System.Reflection.Assembly]::Load" or
+    "[Reflection.Assembly]::Load"
+  )
+'''
+
+
+[[rule.threat]]
+framework = "MITRE ATT&CK"
+
+[[rule.threat.technique]]
+id = "T1055"
+name = "Process Injection"
+reference = "https://attack.mitre.org/techniques/T1055/"
+
+  [[rule.threat.technique.subtechnique]]
+  id = "T1055.001"
+  name = "Dynamic-link Library Injection"
+  reference = "https://attack.mitre.org/techniques/T1055/001/"
+
+  [[rule.threat.technique.subtechnique]]
+  id = "T1055.002"
+  name = "Portable Executable Injection"
+  reference = "https://attack.mitre.org/techniques/T1055/002/"
+
+[rule.threat.tactic]
+id = "TA0005"
+name = "Defense Evasion"
+reference = "https://attack.mitre.org/tactics/TA0005/"
+
+
+[[rule.threat]]
+framework = "MITRE ATT&CK"
+
+[[rule.threat.technique]]
+id = "T1059"
+name = "Command and Scripting Interpreter"
+reference = "https://attack.mitre.org/techniques/T1059/"
+
+    [[rule.threat.technique.subtechnique]]
+    id = "T1059.001"
+    name = "PowerShell"
+    reference = "https://attack.mitre.org/techniques/T1059/001/"
+
+[rule.threat.tactic]
+id = "TA0002"
+name = "Execution"
+reference = "https://attack.mitre.org/tactics/TA0002/"
+