GSA - Detect Protocol Changes for Destination Ports

Status: available
Severity: medium
Time window: 8d
Group by: AlertTimeDstPort, AlertTimeProtocol, DestinationFqdn, SourceIp
Source: github.com/Azure/Azure-Sentinel

Identifies changes in the protocol used for specific destination ports, comparing the current runtime with a learned baseline. This can indicate potential protocol misuse or configuration changes. Configurable Parameters: - Learning period: The time range to establish the baseline. Default is set to 7 days. - Run time: The time range for current analysis. Default is set to 1 day.

MITRE ATT&CK coverage

Tactic	Techniques
Command & Control	`T1571` Non-Standard Port

Rule body kusto

id: f6a8d6a5-3e9f-47c8-a8d5-1b2b9d3b7d6a
name: GSA - Detect Protocol Changes for Destination Ports
description: |
  Identifies changes in the protocol used for specific destination ports, comparing the current runtime with a learned baseline.
  This can indicate potential protocol misuse or configuration changes.
  Configurable Parameters:
  - Learning period: The time range to establish the baseline. Default is set to 7 days.
  - Run time: The time range for current analysis. Default is set to 1 day.
severity: Medium
status: Available
requiredDataConnectors:
  - connectorId: AzureActiveDirectory
    dataTypes:
      - NetworkAccessTrafficLogs
queryFrequency: 1h
queryPeriod: 8d
triggerOperator: gt
triggerThreshold: 1
tactics:
  - DefenseEvasion
  - Exfiltration
  - CommandAndControl
relevantTechniques:
  - T1571
query: |
  let LearningPeriod = 7d;
  let RunTime = 1d;
  let StartLearningPeriod = ago(LearningPeriod + RunTime);
  let EndRunTime = ago(RunTime);
  let LearningPortToProtocol = 
    NetworkAccessTraffic
    | where TimeGenerated between (StartLearningPeriod .. EndRunTime)
    | where isnotempty(DestinationPort)
    | summarize LearningTimeCount = count() by LearningTimeDstPort = DestinationPort, LearningTimeProtocol = TransportProtocol, SourceIp, DestinationFqdn;
  let AlertTimePortToProtocol = 
    NetworkAccessTraffic
    | where TimeGenerated between (EndRunTime .. now())
    | where isnotempty(DestinationPort)
    | summarize AlertTimeCount = count() by AlertTimeDstPort = DestinationPort, AlertTimeProtocol = TransportProtocol, SourceIp, DestinationFqdn;
  AlertTimePortToProtocol
    | join kind=leftouter (LearningPortToProtocol) on $left.AlertTimeDstPort == $right.LearningTimeDstPort and $left.SourceIp == $right.SourceIp and $left.DestinationFqdn == $right.DestinationFqdn
    | where isnotempty(LearningTimeProtocol) and isnotempty(AlertTimeProtocol) and LearningTimeProtocol != AlertTimeProtocol
    | project AlertTimeDstPort, AlertTimeProtocol, LearningTimeProtocol, SourceIp, DestinationFqdn
    | extend IPCustomEntity = SourceIp, FqdnCustomEntity = DestinationFqdn
entityMappings:
  - entityType: IP
    fieldMappings:
      - identifier: Address
        columnName: IPCustomEntity
  - entityType: URL
    fieldMappings:
      - identifier: Url
        columnName: FqdnCustomEntity
version: 1.0.4
kind: Scheduled

Stages and Predicates

Parameters

let LearningPeriod = 7d;
let RunTime = 1d;
let StartLearningPeriod = ago(LearningPeriod + RunTime);
let EndRunTime = ago(RunTime);

Let binding: `LearningPortToProtocol`

let LearningPortToProtocol = NetworkAccessTraffic
  | where TimeGenerated between (StartLearningPeriod .. EndRunTime)
  | where isnotempty(DestinationPort)
  | summarize LearningTimeCount = count() by LearningTimeDstPort = DestinationPort, LearningTimeProtocol = TransportProtocol, SourceIp, DestinationFqdn;

Derived from StartLearningPeriod, EndRunTime.

The stages below define let AlertTimePortToProtocol (the rule's main pipeline source).

Stage 1: `source`

NetworkAccessTraffic

Stage 2: `where`

| where TimeGenerated between (EndRunTime .. now())

Stage 3: `where`

| where isnotempty(DestinationPort)

Stage 4: `summarize`

| summarize AlertTimeCount = count() by AlertTimeDstPort = DestinationPort, AlertTimeProtocol = TransportProtocol, SourceIp, DestinationFqdn

The stages below run on AlertTimePortToProtocol (the outer pipeline).

Stage 5: `join`

AlertTimePortToProtocol
| join kind=leftouter (LearningPortToProtocol) on $left.AlertTimeDstPort == $right.LearningTimeDstPort and $left.SourceIp == $right.SourceIp and $left.DestinationFqdn == $right.DestinationFqdn

Stage 6: `where`

| where isnotempty(LearningTimeProtocol) and isnotempty(AlertTimeProtocol) and LearningTimeProtocol != AlertTimeProtocol

Stage 7: `project`

| project AlertTimeDstPort, AlertTimeProtocol, LearningTimeProtocol, SourceIp, DestinationFqdn

Stage 8: `extend`

| extend IPCustomEntity = SourceIp, FqdnCustomEntity = DestinationFqdn

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
`AlertTimeProtocol`	is_not_null	(no value, null check)
`DestinationPort`	is_not_null	(no value, null check)
`LearningTimeProtocol`	is_not_null	(no value, null check)
`LearningTimeProtocol`	ne	`AlertTimeProtocol` transforms: `cased`
`TimeGenerated`	ge	`StartLearningPeriod`
`TimeGenerated`	le	`EndRunTime`

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
`AlertTimeDstPort`	`project`
`AlertTimeProtocol`	`project`
`DestinationFqdn`	`project`
`LearningTimeProtocol`	`project`
`SourceIp`	`project`
`FqdnCustomEntity`	`extend`
`IPCustomEntity`	`extend`

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`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`
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`-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)
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`"quoted phrase"`	Exact-match a multi-word phrase (free text)

GSA - Detect Protocol Changes for Destination Ports

MITRE ATT&CK coverage

Rule body kusto

Stages and Predicates

Parameters

Let binding: `LearningPortToProtocol`

Stage 1: `source`

Stage 2: `where`

Stage 3: `where`

Stage 4: `summarize`

Stage 5: `join`

Stage 6: `where`

Stage 7: `project`

Stage 8: `extend`

Indicators

Output fields

Keyboard shortcuts

Search operators

GSA - Detect Protocol Changes for Destination Ports

MITRE ATT&CK coverage

Rule body kusto

Stages and Predicates

Parameters

Let binding: LearningPortToProtocol

Stage 1: source

Stage 2: where

Stage 3: where

Stage 4: summarize

Stage 5: join

Stage 6: where

Stage 7: project

Stage 8: extend

Indicators

Output fields

Let binding: `LearningPortToProtocol`

Stage 1: `source`

Stage 2: `where`

Stage 3: `where`

Stage 4: `summarize`

Stage 5: `join`

Stage 6: `where`

Stage 7: `project`

Stage 8: `extend`