SFTP File transfer folder count above threshold

Severity: medium
Time window: 15m
Group by: Computer, src_ip, username
Source: github.com/Azure/Azure-Sentinel

'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.'

MITRE ATT&CK coverage

Tactic	Techniques
Exfiltration	`T1020` Automated Exfiltration

Rule body kusto

id: 7355434e-09d5-4401-b56d-e03e9379dfb1
name: 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
requiredDataConnectors:
  - connectorId: Syslog
    dataTypes:
      - Syslog
  - connectorId: SyslogAma
    dataTypes: 
      - Syslog
queryFrequency: 15m
queryPeriod: 15m
triggerOperator: gt
triggerThreshold: 0
tactics:
  - Exfiltration
relevantTechniques:
  - T1020
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)))))
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
customDetails:
  TransferCount: count_distinct_dirpath
  FilesList: dirlist
incidentConfiguration:
  createIncident: true
  groupingConfiguration:
    enabled: true
    reopenClosedIncident: false
    lookbackDuration: 5h
    matchingMethod: Selected
    groupByEntities:
    - Account
    - Host
    groupByAlertDetails: []
    groupByCustomDetails: []
version: 1.0.2
kind: Scheduled

Stages and Predicates

Parameters

let threshold = 10;

Stage 1: `source`

Syslog

Stage 2: `where`

| where ProcessName has "sftp"
    and SyslogMessage has "close "
    and SyslogMessage has " bytes read "

Stage 3: `parse`

| parse SyslogMessage with "close \"" filepath "\" bytes read " readbytes: int " written " writtenbytes: int

Stage 4: `parse`

| parse kind=regex filepath with dirpath:string "/" filename:string

Stage 5: `join`

| 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

Stage 6: `project-away`

| project-away ProcessID1

Stage 7: `summarize`

| summarize count_distinct_dirpath=dcount(dirpath), dirlist=make_set(dirpath) by Computer, username, src_ip, bin(TimeGenerated, 15m)

Threshold: ge 10

Stage 8: `where`

| where count_distinct_dirpath >= threshold

Stage 9: `extend`

| extend DirSample = iff(array_length(dirlist) == 1, tostring(dirlist[0]), strcat("SeeDirListField","_", tostring(hash(tostring(dirlist)))))

DirSample =

ifdirlist == 1tostring(dirlist[0])

elsestrcat("SeeDirListField", "_", tostring(hash(tostring(dirlist))))

Indicators

Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.

Field	Kind	Values
`ProcessName`	match	`sftp` transforms: `term`
`SyslogMessage`	match	`bytes read` transforms: `term` `close` transforms: `term` `session opened for` transforms: `term`
`count_distinct_dirpath`	ge	`10` transforms: `cased`

Output fields

Fields the rule emits when it matches. Chronicle authors list these in the outcome block; they appear on the detection and $risk_score drives alerting. Sentinel / Defender XDR rules build them up through project / summarize / extend stages. Sentinel maps these into alert fields via entityMappings and customDetails; Defender XDR custom detections surface them as alert fields directly.

Field	Source
`Computer`	`summarize`
`count_distinct_dirpath`	`summarize`
`dirlist`	`summarize`
`src_ip`	`summarize`
`username`	`summarize`
`DirSample`	`extend`

`j` / `k`	Scroll down / up
`d` / `u`	Half-page down / up
`gg` / `G`	Top / bottom
`h` / `l`	History back / forward
`f`	Follow link (`Shift` = new tab)
`/`	Focus search
`?`	Toggle this help
`↑` / `↓`	Navigate search results
`Enter`	Open highlighted result
`Esc`	Close results / dialog

`type:`	`events` / `rules` / `providers`
`vendor:`	`sigma` / `elastic` / `splunk` / `kusto` / `chronicle` (vendor name alone also works: `sigma:`, `kql:`, `secops:`…)
`tactic:`	TA-id, slug, or name: `credential_access`, `TA0006`
`technique:`	technique or sub-technique ID: `T1003`, `T1003.001` (alias `tech:`)
`severity:`	`critical` / `high` / `medium` / `low` / `informational` (alias `sev:`)
`risk_score`	Numeric comparison on the Elastic risk score (0 to 100): `risk_score>50`, `risk_score<=20`, `risk_score=99` (alias `risk`; Elastic rules only)
`stages:`	Rules with exactly N pipeline stages
`correlation:`	`single_event` / `sequence` / `alternatives` / `alternatives_cross_log` / `all_required` / `correlated`
`with:`	Co-occurrence event-id; stacks (`with:4624 with:4769`) to require all, while a comma list in one occurrence (`with:4624,4769`) is an either-or group. Implies multi-event
`like:`	Structural neighbors of a rule slug (equivalents + subsumption stricter / broader): `like:comsvcs_lsass_memory_dump-splunk-sysmon`
`groupby:`	Entity-grouping substring match against `group_by_keys`: `groupby:user`, `groupby:host`
`uses:`	Rules whose predicate tree touches the field (any kind, any value): `uses:CommandLine`
`excludes:`	Rules with top-level `not()` clauses on the field (FP whitelists): `excludes:ParentImage`
`field:` / `value:`	Predicate search; narrows rule cards to those with a matching leaf and drives the indicator tier. Unquoted = substring, wildcards allowed (`value:mimikatz`)
`indicator:`	Shorthand for `field:F value:V`: `indicator:Image=*\powershell.exe`
`kind:`	Filter by predicate kind. Narrows rule cards to those carrying a matching predicate leaf (`vendor:elastic kind:cidr_match`) and drives the indicator tier: `contains` / `starts_with` / `ends_with` / `regex` / `cidr` / `eq` / `in` … (operator aliases `op:`/`match:`)
`has:` / `no:`	`sample`, `field`, `notes`, `refs`, `trace`, `thirdparty`, `rule`, `pattern`, `timewindow`, `threshold`, `newterms`, `sigma`/`elastic`/`splunk`/`kusto`/`chronicle`
`-op:val`	Exclude matches; works on most operators but not `type:`/`like:`/`has:`/`no:` (use `no:<flag>` to exclude a rule flag): `tactic:execution -vendor:splunk`. Standalone `-kind:`/`-field:`/`-value:` drop every rule carrying a matching predicate leaf (`type:rules -kind:is_null`)
`field:"…"` / `value:"…"`	Quoted value = anchored exact match (also allows spaces): `value:"net user"`
`a,b`	Comma = OR inside one operator (`vendor:sigma,elastic`, `severity:high,critical`); repeating a facet merges the same way. `field:`/`value:` never split (literal commas)
`vendors:` / `stage:`	Singular and plural spellings fold to the canonical operator and value: `tactics:` = `tactic:`, `type:event` = `type:events`, `correlation:sequences` = `correlation:sequence`, `has:thresholds` = `has:threshold`
`"quoted phrase"`	Exact-match a multi-word phrase (free text)

SFTP File transfer folder count above threshold

MITRE ATT&CK coverage

Rule body kusto

Stages and Predicates

Parameters

Stage 1: `source`

Stage 2: `where`

Stage 3: `parse`

Stage 4: `parse`

Stage 5: `join`

Stage 6: `project-away`

Stage 7: `summarize`

Stage 8: `where`

Stage 9: `extend`

Indicators

Output fields

Keyboard shortcuts

Search operators

SFTP File transfer folder count above threshold

MITRE ATT&CK coverage

Rule body kusto

Stages and Predicates

Parameters

Stage 1: source

Stage 2: where

Stage 3: parse

Stage 4: parse

Stage 5: join

Stage 6: project-away

Stage 7: summarize

Stage 8: where

Stage 9: extend

Indicators

Output fields

Stage 1: `source`

Stage 2: `where`

Stage 3: `parse`

Stage 4: `parse`

Stage 5: `join`

Stage 6: `project-away`

Stage 7: `summarize`

Stage 8: `where`

Stage 9: `extend`