Abnormal Port to Protocol

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

'Identifies communication for well known protocol over a non-standard port based on learning period activity. This can indicate malicious communication (C2) or exfiltration by attackers trying to communicate over known ports (22:SSH, 80:HTTP) but dont use the known protocol headers to match the port number. Configurable Parameters: - Learning period time - learning period for protocol learning in days. Default is set to 7.'

MITRE ATT&CK coverage

Tactic	Techniques
Command & Control	`T1571` Non-Standard Port, `T1572` Protocol Tunneling
Exfiltration	`T1041` Exfiltration Over C2 Channel

Rule body kusto

id: 826f930c-2f25-4508-8e75-a95b809a4e15
name: Abnormal Port to Protocol
description: |
  'Identifies communication for well known protocol over a non-standard port based on learning period activity. This can indicate malicious communication (C2) or exfiltration by attackers trying to communicate over known ports (22:SSH, 80:HTTP) but dont use the known protocol headers to match the port number.
  
  Configurable Parameters:
  
  - Learning period time - learning period for protocol learning in days. Default is set to 7.'
severity: Medium
status: Available
requiredDataConnectors:
  - connectorId: AzureFirewall
    dataTypes: 
      - AzureDiagnostics
      - AZFWApplicationRule
      - AZFWNetworkRule
queryFrequency: 1h
queryPeriod: 8d
triggerOperator: gt
triggerThreshold: 0
tactics:
  - Exfiltration
  - CommandAndControl
  - DefenseEvasion
relevantTechniques:
  - T1041
  - T1571
  - T1572
query: |
  let LearningPeriod = 7d;
  let RunTime = 1h;
  let StartLearningPeriod = LearningPeriod + RunTime;
  let DetectionWindowStart = ago(RunTime);
  let LearningPortToProtocol1 =  (AzureDiagnostics
  | where TimeGenerated between (ago(StartLearningPeriod) .. ago(RunTime))
  | where OperationName == "AzureFirewallApplicationRuleLog"
  | extend msg_s= column_ifexists('msg_s',Message)
  | parse msg_s with Protocol " request from " SourceIp ":" SourcePort:int " to " Fqdn ":" DestinationPort:int "." *
  | where isnotempty(DestinationPort)
  | summarize LearningTimeCount = count() by LearningTimeDstPort = DestinationPort, LearningTimeProtocol = Protocol, SourceIp, Fqdn);
  let LearningPortToProtocol2 = (AZFWNetworkRule
  | where TimeGenerated between (ago(StartLearningPeriod) .. ago(RunTime))
  | where isnotempty(DestinationPort)
  | extend Fqdn = DestinationIp
  | summarize LearningTimeCount = count() by LearningTimeDstPort = DestinationPort, LearningTimeProtocol = Protocol, SourceIp, Fqdn);
  let LearningPortToProtocol3 = (AZFWApplicationRule
  | where TimeGenerated between (ago(StartLearningPeriod) .. ago(RunTime))
  | where isnotempty(DestinationPort)
  | summarize LearningTimeCount = count() by LearningTimeDstPort = DestinationPort, LearningTimeProtocol = Protocol, SourceIp, Fqdn);
  let AlertTimePortToProtocol1 = (AzureDiagnostics
  | where TimeGenerated between (DetectionWindowStart .. now())
  | where OperationName == "AzureFirewallApplicationRuleLog"
  | extend msg_s= column_ifexists('msg_s',Message)
  | parse msg_s with Protocol " request from " SourceIp ":" SourcePort " to " Fqdn ":" DestinationPort:int "." *
  | where isnotempty(DestinationPort)
  | summarize AlertTimeCount = count() by AlertTimeDstPort = DestinationPort, AlertTimeProtocol = Protocol);
  let AlertTimePortToProtocol2 = (AZFWNetworkRule
  | where TimeGenerated between (DetectionWindowStart .. now())
  | where isnotempty(DestinationPort)
  | extend Fqdn = DestinationIp
  | summarize AlertTimeCount = count() by AlertTimeDstPort = DestinationPort, AlertTimeProtocol = Protocol);
  let AlertTimePortToProtocol3 = (AZFWApplicationRule
  | where TimeGenerated between (DetectionWindowStart .. now())
  | where isnotempty(DestinationPort)
  | summarize AlertTimeCount = count() by AlertTimeDstPort = DestinationPort, AlertTimeProtocol = Protocol);
  (union isfuzzy=true 
  (AlertTimePortToProtocol1 
  | join kind=leftouter (LearningPortToProtocol1) on $left.AlertTimeDstPort == $right.LearningTimeDstPort
  | where LearningTimeProtocol != AlertTimeProtocol),
  (AlertTimePortToProtocol2 
  | join kind=leftouter (LearningPortToProtocol2) on $left.AlertTimeDstPort == $right.LearningTimeDstPort
  | where LearningTimeProtocol != AlertTimeProtocol),
  (AlertTimePortToProtocol3 
  | join kind=leftouter (LearningPortToProtocol3) on $left.AlertTimeDstPort == $right.LearningTimeDstPort
  | where LearningTimeProtocol != AlertTimeProtocol))
entityMappings:
  - entityType: IP
    fieldMappings:
      - identifier: Address
        columnName: SourceIp
  - entityType: URL
    fieldMappings:
      - identifier: Url
        columnName: Fqdn
customDetails:
  AbnormalPort: AlertTimeDstPort
  NetworkProtocol: AlertTimeProtocol
alertDetailsOverride:
  alertDisplayNameFormat: 'Abnormal Port to Protocol Communication Detected from {{SourceIp}} to {{Fqdn}}'
  alertDescriptionFormat: 'Communication was observed over port {{AlertTimeDstPort}} using protocol {{AlertTimeProtocol}}, which is different from the protocol observed during the learning period. This could indicate potential malicious activity such as C2 communication or data exfiltration.'
version: 1.1.4
kind: Scheduled

Stages and Predicates

Parameters

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

Let binding: `LearningPortToProtocol1`

let LearningPortToProtocol1 = (AzureDiagnostics
| where TimeGenerated between (ago(StartLearningPeriod) .. ago(RunTime))
| where OperationName == "AzureFirewallApplicationRuleLog"
| extend msg_s= column_ifexists('msg_s',Message)
| parse msg_s with Protocol " request from " SourceIp ":" SourcePort:int " to " Fqdn ":" DestinationPort:int "." *
| where isnotempty(DestinationPort)
| summarize LearningTimeCount = count() by LearningTimeDstPort = DestinationPort, LearningTimeProtocol = Protocol, SourceIp, Fqdn);

Derived from RunTime, StartLearningPeriod.

Let binding: `LearningPortToProtocol2`

let LearningPortToProtocol2 = (AZFWNetworkRule
| where TimeGenerated between (ago(StartLearningPeriod) .. ago(RunTime))
| where isnotempty(DestinationPort)
| extend Fqdn = DestinationIp
| summarize LearningTimeCount = count() by LearningTimeDstPort = DestinationPort, LearningTimeProtocol = Protocol, SourceIp, Fqdn);

Derived from RunTime, StartLearningPeriod.

Let binding: `LearningPortToProtocol3`

let LearningPortToProtocol3 = (AZFWApplicationRule
| where TimeGenerated between (ago(StartLearningPeriod) .. ago(RunTime))
| where isnotempty(DestinationPort)
| summarize LearningTimeCount = count() by LearningTimeDstPort = DestinationPort, LearningTimeProtocol = Protocol, SourceIp, Fqdn);

Derived from RunTime, StartLearningPeriod.

Let binding: `AlertTimePortToProtocol1`

let AlertTimePortToProtocol1 = (AzureDiagnostics
| where TimeGenerated between (DetectionWindowStart .. now())
| where OperationName == "AzureFirewallApplicationRuleLog"
| extend msg_s= column_ifexists('msg_s',Message)
| parse msg_s with Protocol " request from " SourceIp ":" SourcePort " to " Fqdn ":" DestinationPort:int "." *
| where isnotempty(DestinationPort)
| summarize AlertTimeCount = count() by AlertTimeDstPort = DestinationPort, AlertTimeProtocol = Protocol);

Derived from DetectionWindowStart.

Let binding: `AlertTimePortToProtocol2`

let AlertTimePortToProtocol2 = (AZFWNetworkRule
| where TimeGenerated between (DetectionWindowStart .. now())
| where isnotempty(DestinationPort)
| extend Fqdn = DestinationIp
| summarize AlertTimeCount = count() by AlertTimeDstPort = DestinationPort, AlertTimeProtocol = Protocol);

Derived from DetectionWindowStart.

Let binding: `AlertTimePortToProtocol3`

let AlertTimePortToProtocol3 = (AZFWApplicationRule
| where TimeGenerated between (DetectionWindowStart .. now())
| where isnotempty(DestinationPort)
| summarize AlertTimeCount = count() by AlertTimeDstPort = DestinationPort, AlertTimeProtocol = Protocol);

Derived from DetectionWindowStart.

union `isfuzzy=true` (3 sources)

Each leg below queries one source; the rule matches if any leg does. Sources: AlertTimePortToProtocol1, AlertTimePortToProtocol2, AlertTimePortToProtocol3

Leg 1: `AlertTimePortToProtocol1`

AlertTimePortToProtocol1 
| join kind=leftouter (LearningPortToProtocol1) on $left.AlertTimeDstPort == $right.LearningTimeDstPort
| where LearningTimeProtocol != AlertTimeProtocol

Leg 2: `AlertTimePortToProtocol2`

AlertTimePortToProtocol2 
| join kind=leftouter (LearningPortToProtocol2) on $left.AlertTimeDstPort == $right.LearningTimeDstPort
| where LearningTimeProtocol != AlertTimeProtocol

Leg 3: `AlertTimePortToProtocol3`

AlertTimePortToProtocol3 
| join kind=leftouter (LearningPortToProtocol3) on $left.AlertTimeDstPort == $right.LearningTimeDstPort
| where LearningTimeProtocol != AlertTimeProtocol

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
`DestinationPort`	is_not_null	(no value, null check)
`LearningTimeProtocol`	ne	`AlertTimeProtocol` transforms: `cased`
`OperationName`	eq	`AzureFirewallApplicationRuleLog` 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
`Fqdn`	`summarize`
`LearningTimeDstPort`	`summarize`
`LearningTimeProtocol`	`summarize`
`SourceIp`	`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)

Abnormal Port to Protocol

MITRE ATT&CK coverage

Rule body kusto

Stages and Predicates

Parameters

Let binding: `LearningPortToProtocol1`

Let binding: `LearningPortToProtocol2`

Let binding: `LearningPortToProtocol3`

Let binding: `AlertTimePortToProtocol1`

Let binding: `AlertTimePortToProtocol2`

Let binding: `AlertTimePortToProtocol3`

union `isfuzzy=true` (3 sources)

Leg 1: `AlertTimePortToProtocol1`

Leg 2: `AlertTimePortToProtocol2`

Leg 3: `AlertTimePortToProtocol3`

Indicators

Output fields

Keyboard shortcuts

Search operators

Abnormal Port to Protocol

MITRE ATT&CK coverage

Rule body kusto

Stages and Predicates

Parameters

Let binding: LearningPortToProtocol1

Let binding: LearningPortToProtocol2

Let binding: LearningPortToProtocol3

Let binding: AlertTimePortToProtocol1

Let binding: AlertTimePortToProtocol2

Let binding: AlertTimePortToProtocol3

union isfuzzy=true (3 sources)

Leg 1: AlertTimePortToProtocol1

Leg 2: AlertTimePortToProtocol2

Leg 3: AlertTimePortToProtocol3

Indicators

Output fields

Let binding: `LearningPortToProtocol1`

Let binding: `LearningPortToProtocol2`

Let binding: `LearningPortToProtocol3`

Let binding: `AlertTimePortToProtocol1`

Let binding: `AlertTimePortToProtocol2`

Let binding: `AlertTimePortToProtocol3`

union `isfuzzy=true` (3 sources)

Leg 1: `AlertTimePortToProtocol1`

Leg 2: `AlertTimePortToProtocol2`

Leg 3: `AlertTimePortToProtocol3`