Base64 encoded Windows process command-lines Normalized Process Events

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Id	f8b3c49c-4087-499b-920f-0dcfaff0cbca
Rulename	Base64 encoded Windows process command-lines (Normalized Process Events)
Description	Identifies instances of a base64 encoded PE file header seen in the process command line parameter. To use this analytics rule, make sure you have deployed the ASIM normalization parsers
Severity	Medium
Tactics	Execution DefenseEvasion
Techniques	T1059 T1027 T1140
Kind	Scheduled
Query frequency	1d
Query period	1d
Trigger threshold	0
Trigger operator	gt
Source Uri	https://github.com/Azure/Azure-Sentinel/blob/master/Detections/ASimProcess/imProcess_base64_encoded_pefile.yaml
Version	1.1.4
Arm template	f8b3c49c-4087-499b-920f-0dcfaff0cbca.json

KQL

imProcessCreate
| where CommandLine contains "TVqQAAMAAAAEAAA"
| where isnotempty(Process)
| summarize StartTime = min(TimeGenerated), EndTime = max(TimeGenerated), count() by Dvc, ActorUsername, Process, CommandLine, ActingProcessName, EventVendor, EventProduct
| extend AccountName = tostring(split(ActorUsername, @'\')[1]), AccountNTDomain = tostring(split(ActorUsername, @'\')[0])
| extend HostName = tostring(split(Dvc, ".")[0]), DomainIndex = toint(indexof(Dvc, '.'))
| extend HostNameDomain = iff(DomainIndex != -1, substring(Dvc, DomainIndex + 1), Dvc)
| project-away DomainIndex

YAML

description: |
  'Identifies instances of a base64 encoded PE file header seen in the process command line parameter.
  To use this analytics rule, make sure you have deployed the [ASIM normalization parsers](https://aka.ms/ASimProcessEvent)'  
kind: Scheduled
tactics:
- Execution
- DefenseEvasion
requiredDataConnectors: []
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Detections/ASimProcess/imProcess_base64_encoded_pefile.yaml
severity: Medium
name: Base64 encoded Windows process command-lines (Normalized Process Events)
metadata:
  support:
    tier: Community
  author:
    name: Yuval Naor
  categories:
    domains:
    - Security - Threat Protection
  source:
    kind: Community
triggerThreshold: 0
queryPeriod: 1d
query: |
  imProcessCreate
  | where CommandLine contains "TVqQAAMAAAAEAAA"
  | where isnotempty(Process)
  | summarize StartTime = min(TimeGenerated), EndTime = max(TimeGenerated), count() by Dvc, ActorUsername, Process, CommandLine, ActingProcessName, EventVendor, EventProduct
  | extend AccountName = tostring(split(ActorUsername, @'\')[1]), AccountNTDomain = tostring(split(ActorUsername, @'\')[0])
  | extend HostName = tostring(split(Dvc, ".")[0]), DomainIndex = toint(indexof(Dvc, '.'))
  | extend HostNameDomain = iff(DomainIndex != -1, substring(Dvc, DomainIndex + 1), Dvc)
  | project-away DomainIndex  
relevantTechniques:
- T1059
- T1027
- T1140
id: f8b3c49c-4087-499b-920f-0dcfaff0cbca
queryFrequency: 1d
entityMappings:
- entityType: Account
  fieldMappings:
  - columnName: ActorUsername
    identifier: FullName
  - columnName: AccountName
    identifier: Name
  - columnName: AccountNTDomain
    identifier: NTDomain
- entityType: Host
  fieldMappings:
  - columnName: Dvc
    identifier: FullName
  - columnName: HostName
    identifier: HostName
  - columnName: HostNameDomain
    identifier: DnsDomain
triggerOperator: gt
version: 1.1.4
tags:
- Id: ca67c83e-7fff-4127-a3e3-1af66d6d4cad
  version: 1.0.0
- Schema: ASIMProcessEvent
  SchemaVersion: 0.1.0

ARM