CTERA Mass Access Denied Detection Analytic

Status: available
Severity: high
Time window: 5m
Group by: EdgeFiler, UserName
Source: github.com/Azure/Azure-Sentinel

This analytic rule detects and alerts when access denied operations generated by the CTERA Edge Filer goes over a predefined threshold

MITRE ATT&CK coverage

Tactic	Techniques
Stealth	`T1562` Impair Defenses

Rule body kusto

id: 88341fc3-38e1-46db-8bb1-6c052e749991
name: CTERA Mass Access Denied Detection Analytic
description: 'This analytic rule detects and alerts when access denied operations generated by the CTERA Edge Filer goes over a predefined threshold'
kind: Scheduled
severity: High
status: Available
requiredDataConnectors:
  - connectorId: CTERA
    dataTypes:
      - Syslog
queryFrequency: 5m
queryPeriod: 5m
triggerOperator: GreaterThan
triggerThreshold: 1000
tactics:
  - DefenseEvasion
relevantTechniques:
  - T1562
query: |
  Syslog
  | where ProcessName == 'gw-audit'
  | extend
      TenantName = extract("\"vportal\":\"([^\"]*)\"", 1, SyslogMessage),
      UserName = extract("user=([^|]*)", 1, SyslogMessage),
      Operation = extract("op=([^|]*)", 1, SyslogMessage),
      EdgeFiler = extract("\"client\":\"([^\"]*)\"", 1, SyslogMessage),
      RootPath = extract("rootPath=([^|]*)", 1, SyslogMessage),
      Share = extract("share=([^|]*)", 1, SyslogMessage),
      LocalPath = extract("path=([^|]*)", 1, SyslogMessage),
      Timestamp = todatetime(extract("\"@timestamp\":\"([^\"]*)\"", 1, SyslogMessage))
  | where Operation in ('OpenDenied', 'createDenied', 'AclDenied', 'deleteDenied')
  | summarize Count = count() by bin(Timestamp, 5m), UserName, EdgeFiler
  | where Count > 1000
incidentConfiguration:
    createIncident: true
    groupingConfiguration:
        enabled: false
        reopenClosedIncident: false
        lookbackDuration: PT5H
        matchingMethod: AllEntities
eventGroupingSettings:
    aggregationKind: SingleAlert
alertDetailsOverride:
    alertnameFormat: 'CTERA Batch Access Denied Detection'
    alertDescriptionFormat: >
      Detected {{Count}} denied access attempts by user {{UserName}} on Edge Filer 
      {{EdgeFiler}} within 5 minutes. Please investigate unauthorized access attempts or misconfigurations.
customDetails:
    TenantName: TenantName
    UserName: UserName
    EdgeFiler: EdgeFiler
    RootPath: RootPath
    Share: Share
entityMappings:
  - entityType: Account
    fieldMappings:
      - identifier: Name
        columnName: UserName
  - entityType: File
    fieldMappings:
      - identifier: Name
        columnName: EdgeFiler
suppressionDuration: PT5H
suppressionEnabled: false
version: 1.0.0

Stages and Predicates

Stage 1: `source`

Syslog

Stage 2: `where`

| where ProcessName == 'gw-audit'

Stage 3: `extend`

| extend
    TenantName = extract("\"vportal\":\"([^\"]*)\"", 1, SyslogMessage),
    UserName = extract("user=([^|]*)", 1, SyslogMessage),
    Operation = extract("op=([^|]*)", 1, SyslogMessage),
    EdgeFiler = extract("\"client\":\"([^\"]*)\"", 1, SyslogMessage),
    RootPath = extract("rootPath=([^|]*)", 1, SyslogMessage),
    Share = extract("share=([^|]*)", 1, SyslogMessage),
    LocalPath = extract("path=([^|]*)", 1, SyslogMessage),
    Timestamp = todatetime(extract("\"@timestamp\":\"([^\"]*)\"", 1, SyslogMessage))

Stage 4: `where`

| where Operation in ('OpenDenied', 'createDenied', 'AclDenied', 'deleteDenied')

Stage 5: `summarize`

| summarize Count = count() by bin(Timestamp, 5m), UserName, EdgeFiler

Threshold: gt 1000

Stage 6: `where`

| where Count > 1000

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
`Count`	gt	`1000` transforms: `cased`
`Operation`	in	`AclDenied` transforms: `cased` `OpenDenied` transforms: `cased` `createDenied` transforms: `cased` `deleteDenied` transforms: `cased`
`ProcessName`	eq	`gw-audit` 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
`Count`	`summarize`
`EdgeFiler`	`summarize`
`UserName`	`summarize`

`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)

CTERA Mass Access Denied Detection Analytic

MITRE ATT&CK coverage

Rule body kusto

Stages and Predicates

Stage 1: `source`

Stage 2: `where`

Stage 3: `extend`

Stage 4: `where`

Stage 5: `summarize`

Stage 6: `where`

Indicators

Output fields

Keyboard shortcuts

Search operators

CTERA Mass Access Denied Detection Analytic

MITRE ATT&CK coverage

Rule body kusto

Stages and Predicates

Stage 1: source

Stage 2: where

Stage 3: extend

Stage 4: where

Stage 5: summarize

Stage 6: where

Indicators

Output fields

Stage 1: `source`

Stage 2: `where`

Stage 3: `extend`

Stage 4: `where`

Stage 5: `summarize`

Stage 6: `where`