Process Creation with Suspicious CommandLine Arguments

id: fdbcc0eb-44fb-467e-a51d-a91df0780a81
name: 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
status: Available 
tags:
  - Schema: _ASim_ProcessEvent
    SchemaVersion: 0.1.4
requiredDataConnectors:
  - connectorId: CrowdStrikeFalconEndpointProtection
    dataTypes: 
      - CommonSecurityLog
  - connectorId: MicrosoftThreatProtection
    dataTypes:
      - SecurityAlert
  - connectorId: SentinelOne
    dataTypes:
      - SentinelOne_CL
  - connectorId: VMwareCarbonBlack
    dataTypes:
      - CarbonBlackEvents_CL
  - connectorId: CiscoSecureEndpoint
    dataTypes:
      - CiscoSecureEndpoint_CL
  - connectorId: TrendMicroApexOne
    dataTypes:
      - TMApexOneEvent
  - connectorId: TrendMicroApexOneAma
    dataTypes:
      - TMApexOneEvent
queryFrequency: 1h
queryPeriod: 1h
triggerOperator: gt
triggerThreshold: 0
tactics:
  - Execution
  - DefenseEvasion
relevantTechniques:
  - T1059
  - T1027
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]), '')
entityMappings:
  - entityType: Host
    fieldMappings:
      - identifier: HostName
        columnName: DvcHostname
      - identifier: DnsDomain
        columnName: DvcDomain
      - identifier: NTDomain
        columnName: NTDomain
  - entityType: IP
    fieldMappings:
      - identifier: Address
        columnName: DvcIpAddr
  - entityType: Account
    fieldMappings:
      - identifier: Name
        columnName: Username
      - identifier: UPNSuffix
        columnName: UPNSuffix
      - identifier: NTDomain
        columnName: NTDomain
  - entityType: Process
    fieldMappings:
      - identifier: ProcessId
        columnName: TargetProcessId
      - identifier: CommandLine
        columnName: CommandLine
eventGroupingSettings:
  aggregationKind: AlertPerResult
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."
version: 1.0.1
kind: Scheduled