Detection rules › Kusto
Trend Micro CAS - Unexpected file on file share
'Detects unexpected files on file share.'
MITRE ATT&CK coverage
| Tactic | Techniques |
|---|---|
| Initial Access |
Rule body
id: de54f817-f338-46bf-989b-4e016ea6b71b
name: Trend Micro CAS - Unexpected file on file share
description: |
'Detects unexpected files on file share.'
severity: Medium
status: Available
requiredDataConnectors:
- connectorId: TrendMicroCAS
dataTypes:
- TrendMicroCAS
queryFrequency: 1h
queryPeriod: 1h
triggerOperator: gt
triggerThreshold: 0
tactics:
- InitialAccess
relevantTechniques:
- T1566
query: |
let f_types = dynamic(['ps1', 'bat', 'scr', 'sh', 'exe', 'js', 'lnk']);
TrendMicroCAS
| where EventCategoryType in~ ('sharepoint', 'onedrive', 'dropbox', 'box', 'googledrive')
| where isnotempty(SrcFileName)
| extend file_type = extract(@'\.(\w+)$', 1, SrcFileName)
| where file_type in~ (f_types) or SrcFileName !contains @'.'
| extend AccountCustomEntity = DstUserName
entityMappings:
- entityType: Account
fieldMappings:
- identifier: Name
columnName: AccountCustomEntity
version: 1.0.0
kind: Scheduled
Stages and Predicates
Parameters
let f_types = dynamic(['ps1', 'bat', 'scr', 'sh', 'exe', 'js', 'lnk']);
Stage 1: source
TrendMicroCAS
Stage 2: where
| where EventCategoryType in~ ('sharepoint', 'onedrive', 'dropbox', 'box', 'googledrive')
Stage 3: where
| where isnotempty(SrcFileName)
Stage 4: extend
| extend file_type = extract(@'\.(\w+)$', 1, SrcFileName)
Stage 5: where
| where file_type in~ (f_types) or SrcFileName !contains @'.'
Stage 6: extend
| extend AccountCustomEntity = DstUserName
Indicators
These rows show field, operator, and value matches.
| Field | Kind | Values | Search |
|---|---|---|---|
EventCategoryType | in |
| field:"EventCategoryType" kind:in |
SrcFileName | is_not_null | field:"SrcFileName" kind:is_not_null | |
file_type | in |
| field:"file_type" kind:in |
Output fields
These fields are emitted when the rule matches.
| Field | Source |
|---|---|
file_type | extend |
AccountCustomEntity | extend |