Process Creation with Suspicious CommandLine Arguments

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Id	fdbcc0eb-44fb-467e-a51d-a91df0780a81
Rulename	Process Creation with Suspicious CommandLine Arguments
Description	This analytic rule detects process creation events with base64 encoded command line arguments. This could be an indication of a malicious process being executed.
Severity	Medium
Tactics	Execution DefenseEvasion
Techniques	T1059 T1027
Required data connectors	CiscoSecureEndpoint CrowdStrikeFalconEndpointProtection MicrosoftThreatProtection SentinelOne TrendMicroApexOne TrendMicroApexOneAma VMwareCarbonBlack
Kind	Scheduled
Query frequency	1h
Query period	1h
Trigger threshold	0
Trigger operator	gt
Source Uri	https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Malware Protection Essentials/Analytic Rules/SuspiciousProcessCreation.yaml
Version	1.0.1
Arm template	fdbcc0eb-44fb-467e-a51d-a91df0780a81.json

KQL

_ASim_ProcessEvent
| where EventType == 'ProcessCreated'
| extend CommandLineArgs = strcat_array(array_slice(split(CommandLine, " "), 1, -1), " ")
| where strlen(CommandLineArgs) > 0
| where CommandLineArgs contains "base64"
| project
TimeGenerated,
DvcHostname,
DvcIpAddr,
DvcDomain,
TargetUsername,
TargetUsernameType,
TargetProcessName,
TargetProcessId,
CommandLine
| extend Username = iff(tostring(TargetUsernameType) == 'Windows', tostring(split(TargetUsername, '\\')[1]), TargetUsername)
| extend NTDomain = iff(tostring(TargetUsernameType) == 'Windows', tostring(split(TargetUsername, '\\')[0]), TargetUsername)
| extend Username = iff(tostring(TargetUsernameType) == 'UPN', tostring(split(TargetUsername, '@')[0]), Username)
| extend UPNSuffix = iff(tostring(TargetUsernameType) == 'UPN', tostring(split(TargetUsername, '@')[1]), '')

YAML

entityMappings:
- fieldMappings:
  - columnName: DvcHostname
    identifier: HostName
  - columnName: DvcDomain
    identifier: DnsDomain
  - columnName: NTDomain
    identifier: NTDomain
  entityType: Host
- fieldMappings:
  - columnName: DvcIpAddr
    identifier: Address
  entityType: IP
- fieldMappings:
  - columnName: Username
    identifier: Name
  - columnName: UPNSuffix
    identifier: UPNSuffix
  - columnName: NTDomain
    identifier: NTDomain
  entityType: Account
- fieldMappings:
  - columnName: TargetProcessId
    identifier: ProcessId
  - columnName: CommandLine
    identifier: CommandLine
  entityType: Process
name: Process Creation with Suspicious CommandLine Arguments
triggerThreshold: 0
alertDetailsOverride:
  alertDisplayNameFormat: Process with suspicious command line arguments was created on {{DvcHostname}} ({{DvcIpAddr}}) by ({{TargetUsername}})
  alertDescriptionFormat: "Process '{{TargetProcessName}}' ProcessId: '{{TargetProcessId}}' with commandline {{CommandLine}} was created."
eventGroupingSettings:
  aggregationKind: AlertPerResult
triggerOperator: gt
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Malware Protection Essentials/Analytic Rules/SuspiciousProcessCreation.yaml
id: fdbcc0eb-44fb-467e-a51d-a91df0780a81
kind: Scheduled
status: Available
queryFrequency: 1h
severity: Medium
description: |
    This analytic rule detects process creation events with base64 encoded command line arguments. This could be an indication of a malicious process being executed.
query: |
  _ASim_ProcessEvent
  | where EventType == 'ProcessCreated'
  | extend CommandLineArgs = strcat_array(array_slice(split(CommandLine, " "), 1, -1), " ")
  | where strlen(CommandLineArgs) > 0
  | where CommandLineArgs contains "base64"
  | project
  TimeGenerated,
  DvcHostname,
  DvcIpAddr,
  DvcDomain,
  TargetUsername,
  TargetUsernameType,
  TargetProcessName,
  TargetProcessId,
  CommandLine
  | extend Username = iff(tostring(TargetUsernameType) == 'Windows', tostring(split(TargetUsername, '\\')[1]), TargetUsername)
  | extend NTDomain = iff(tostring(TargetUsernameType) == 'Windows', tostring(split(TargetUsername, '\\')[0]), TargetUsername)
  | extend Username = iff(tostring(TargetUsernameType) == 'UPN', tostring(split(TargetUsername, '@')[0]), Username)
  | extend UPNSuffix = iff(tostring(TargetUsernameType) == 'UPN', tostring(split(TargetUsername, '@')[1]), '')  
version: 1.0.1
tactics:
- Execution
- DefenseEvasion
tags:
- SchemaVersion: 0.1.4
  Schema: _ASim_ProcessEvent
queryPeriod: 1h
relevantTechniques:
- T1059
- T1027
requiredDataConnectors:
- dataTypes:
  - CommonSecurityLog
  connectorId: CrowdStrikeFalconEndpointProtection
- dataTypes:
  - SecurityAlert
  connectorId: MicrosoftThreatProtection
- dataTypes:
  - SentinelOne_CL
  connectorId: SentinelOne
- dataTypes:
  - CarbonBlackEvents_CL
  connectorId: VMwareCarbonBlack
- dataTypes:
  - CiscoSecureEndpoint_CL
  connectorId: CiscoSecureEndpoint
- dataTypes:
  - TMApexOneEvent
  connectorId: TrendMicroApexOne
- dataTypes:
  - TMApexOneEvent
  connectorId: TrendMicroApexOneAma

ARM