SFTP File transfer folder count above threshold

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Id	7355434e-09d5-4401-b56d-e03e9379dfb1
Rulename	SFTP File transfer folder count above threshold
Description	Identifies SFTP File Transfers with distinct folder count above certain threshold in a 15min time period. It requires SFTP VERBOSE loglevel to be enabled. Please note that entity mapping for arrays is not supported, so when there is a single value in an array, we will pull that value from the array as a single string to populate the entity to support entity mapping features within Sentinel. Additionally, if the array is multivalued, we will input a string to indicate this with a unique hash so that matching will not occur.
Severity	Medium
Tactics	Exfiltration
Techniques	T1020
Required data connectors	Syslog SyslogAma
Kind	Scheduled
Query frequency	15m
Query period	15m
Trigger threshold	0
Trigger operator	gt
Source Uri	https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Syslog/Analytic Rules/sftp_file_transfer_folders_above_threshold.yaml
Version	1.0.2
Arm template	7355434e-09d5-4401-b56d-e03e9379dfb1.json

KQL

let threshold = 10;
Syslog
| where ProcessName has "sftp"
    and SyslogMessage has "close "
    and SyslogMessage has " bytes read "
| parse SyslogMessage with "close \"" filepath "\" bytes read " readbytes: int " written " writtenbytes: int
| parse kind=regex filepath with dirpath:string "/" filename:string
| join kind=leftouter (
    Syslog
    | where ProcessName has "sftp" and SyslogMessage has "session opened for"
    | parse SyslogMessage with "session opened for local user " username: string " from [" src_ip "]"
    | project username, src_ip, ProcessID
    )
    on ProcessID
| project-away ProcessID1
| summarize count_distinct_dirpath=dcount(dirpath), dirlist=make_set(dirpath) by Computer, username, src_ip, bin(TimeGenerated, 15m)
| where count_distinct_dirpath >= threshold
| extend DirSample = iff(array_length(dirlist) == 1, tostring(dirlist[0]), strcat("SeeDirListField","_", tostring(hash(tostring(dirlist)))))

YAML

queryFrequency: 15m
incidentConfiguration:
  groupingConfiguration:
    lookbackDuration: 5h
    reopenClosedIncident: false
    groupByCustomDetails: []
    matchingMethod: Selected
    groupByAlertDetails: []
    groupByEntities:
    - Account
    - Host
    enabled: true
  createIncident: true
tactics:
- Exfiltration
name: SFTP File transfer folder count above threshold
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Syslog/Analytic Rules/sftp_file_transfer_folders_above_threshold.yaml
triggerThreshold: 0
description: |
  'Identifies SFTP File Transfers with distinct folder count above certain threshold in a 15min time period.
   It requires SFTP VERBOSE loglevel to be enabled.
   Please note that entity mapping for arrays is not supported, so when there is a single value in an array, we will pull that value from the array as a single string to populate the entity to support entity mapping features within Sentinel. Additionally, if the array is multivalued, we will input a string to indicate this with a unique hash so that matching will not occur.'  
kind: Scheduled
entityMappings:
- entityType: Account
  fieldMappings:
  - identifier: Name
    columnName: username
- entityType: IP
  fieldMappings:
  - identifier: Address
    columnName: src_ip
- entityType: Host
  fieldMappings:
  - identifier: HostName
    columnName: Computer
- entityType: File
  fieldMappings:
  - identifier: Name
    columnName: DirSample
id: 7355434e-09d5-4401-b56d-e03e9379dfb1
customDetails:
  FilesList: dirlist
  TransferCount: count_distinct_dirpath
queryPeriod: 15m
version: 1.0.2
severity: Medium
relevantTechniques:
- T1020
requiredDataConnectors:
- connectorId: Syslog
  dataTypes:
  - Syslog
- connectorId: SyslogAma
  dataTypes:
  - Syslog
triggerOperator: gt
query: |
  let threshold = 10;
  Syslog
  | where ProcessName has "sftp"
      and SyslogMessage has "close "
      and SyslogMessage has " bytes read "
  | parse SyslogMessage with "close \"" filepath "\" bytes read " readbytes: int " written " writtenbytes: int
  | parse kind=regex filepath with dirpath:string "/" filename:string
  | join kind=leftouter (
      Syslog
      | where ProcessName has "sftp" and SyslogMessage has "session opened for"
      | parse SyslogMessage with "session opened for local user " username: string " from [" src_ip "]"
      | project username, src_ip, ProcessID
      )
      on ProcessID
  | project-away ProcessID1
  | summarize count_distinct_dirpath=dcount(dirpath), dirlist=make_set(dirpath) by Computer, username, src_ip, bin(TimeGenerated, 15m)
  | where count_distinct_dirpath >= threshold
  | extend DirSample = iff(array_length(dirlist) == 1, tostring(dirlist[0]), strcat("SeeDirListField","_", tostring(hash(tostring(dirlist)))))

ARM