Microsoft Entra ID UserAgent OS Missmatch

Status: available
Severity: medium
Time window: 1d
Group by: DeviceOS, UserAgentOS, UserPrincipalName
Source: github.com/Azure/Azure-Sentinel

This query extracts the operating system from the UserAgent header and compares this to the DeviceDetail information present in Microsoft Entra ID.

MITRE ATT&CK coverage

Tactic	Techniques
Stealth	`T1036` Masquerading

Rules detecting the same action

Other rules on this platform that filter on the same API call or operation.

Anomalous sign-in location by user account and authenticating application (Kusto)
Anomalous Single Factor Signin (Kusto)
Authentications of Privileged Accounts Outside of Expected Controls (Kusto)
Azure Many Failed SignIns (Panther)
Azure Portal sign in from another Azure Tenant (Kusto)
Azure Service Principal Sign-In Followed by Arc Cluster Credential Access (Elastic)
Azure SignIn via Legacy Authentication Protocol (Panther)
Detect non-admin requesting token for admin applications (Kusto)

Rule body kusto

id: 6a638d80-f6b2-473b-9087-3cac78a84b40
name: Microsoft Entra ID UserAgent OS Missmatch
description: |
  This query extracts the operating system from the UserAgent header and compares this to the DeviceDetail information present in Microsoft Entra ID.
severity: Medium
status: Available
requiredDataConnectors:
  - connectorId: AzureActiveDirectory
    dataTypes:
      - SigninLogs
  - connectorId: AzureActiveDirectory
    dataTypes:
      - AADNonInteractiveUserSignInLogs
queryFrequency: 1d
queryPeriod: 1d
triggerOperator: gt
triggerThreshold: 0
tactics:
  - DefenseEvasion
relevantTechniques:
  - T1036
query: |
  let timeframe = 1d;
  let ExtractOSFromUA=(ua:string) {
      case(
          ua has "Windows NT 6.0", "Windows Vista/Windows Server 2008",
          ua has "Windows NT 6.1", "Windows 7/Windows Server 2008R2",
          ua has "Windows NT 6.1", "Windows 7/Windows Server 2008",
          ua has "Windows NT 6.2", "Windows 8/Windows Server 2012",
          ua has "Windows NT 6.3", "Windows 8.1/Windows Server 2012R2",
          ua has "Windows NT 10.0", "Windows 10",
          ua has "Windows NT 11.0", "Windows 11",
          ua has "Windows Phone", "WindowsPhone",
          ua has "Android", "Android",
          ua has "iPhone;", "IOS",
          ua has "iPad;", "IOS",
          ua has "Polycom/", "Polycom",
          ua has "Darwin/", "MacOS",
          ua has "Mac OS X", "MacOS",
          ua has "macOS", "MacOS",
          ua has "ubuntu", "Linux",
          ua has "Linux", "Linux",
          ua has "curl", "CLI",
          ua has "python", "CLI",
          "Unknown"
      )
  };
  // Query to obtain 'simplified' user agents in a given timespan.
  union withsource=tbl_name AADNonInteractiveUserSignInLogs, SigninLogs
  | where TimeGenerated >= ago(timeframe)
  | extend UserAgentOS=tolower(ExtractOSFromUA(UserAgent))
  | where not(isempty(UserAgent))
  | where not(isempty(AppId))
  | where ResultType == 0
  | extend DeviceOS=tolower(DeviceDetail_dynamic.operatingSystem)
  | where not(isempty(DeviceOS))
  | where not(UserAgentOS == "unknown")
  // Look for matches both ways, since sometimes the browser OS is more specific and sometimes the DeviceOS is more specific.
  | where not(UserAgentOS contains DeviceOS) and not(DeviceOS contains UserAgentOS)
  | where not(DeviceOS == "ios" and UserAgentOS == "macos") // This can happen for 'request desktop site'
  | where not(DeviceOS == "android" and UserAgentOS == "linux") // Android and Linux sometimes confused
  | summarize count(), arg_min(TimeGenerated,*) by DeviceOS, UserAgentOS, UserPrincipalName
  // Begin allow-list.
  // End allow-list.
entityMappings:
  - entityType: Account
    fieldMappings:
      - identifier: FullName
        columnName: UserPrincipalName
version: 1.0.2
kind: Scheduled

Stages and Predicates

Parameters

let timeframe = 1d;

Let binding: `ExtractOSFromUA`

let ExtractOSFromUA = (ua:string) {
    case(
        ua has "Windows NT 6.0", "Windows Vista/Windows Server 2008",
        ua has "Windows NT 6.1", "Windows 7/Windows Server 2008R2",
        ua has "Windows NT 6.1", "Windows 7/Windows Server 2008",
        ua has "Windows NT 6.2", "Windows 8/Windows Server 2012",
        ua has "Windows NT 6.3", "Windows 8.1/Windows Server 2012R2",
        ua has "Windows NT 10.0", "Windows 10",
        ua has "Windows NT 11.0", "Windows 11",
        ua has "Windows Phone", "WindowsPhone",
        ua has "Android", "Android",
        ua has "iPhone;", "IOS",
        ua has "iPad;", "IOS",
        ua has "Polycom/", "Polycom",
        ua has "Darwin/", "MacOS",
        ua has "Mac OS X", "MacOS",
        ua has "macOS", "MacOS",
        ua has "ubuntu", "Linux",
        ua has "Linux", "Linux",
        ua has "curl", "CLI",
        ua has "python", "CLI",
        "Unknown"
    )
};

union `withsource=tbl_name` (2 sources)

Each leg below queries one source; the rule matches if any leg does. Sources: AADNonInteractiveUserSignInLogs, SigninLogs

Leg 1: `AADNonInteractiveUserSignInLogs`

Leg 2: `SigninLogs`

Applied to the combined result

| where TimeGenerated >= ago(timeframe) | extend UserAgentOS=tolower(ExtractOSFromUA(UserAgent)) | where not(isempty(UserAgent)) | where not(isempty(AppId)) | where ResultType == 0 | extend DeviceOS=tolower(DeviceDetail_dynamic.operatingSystem) | where not(isempty(DeviceOS)) | where not(UserAgentOS == "unknown") | where not(UserAgentOS contains DeviceOS) and not(DeviceOS contains UserAgentOS) | where not(DeviceOS == "ios" and UserAgentOS == "macos") | where not(DeviceOS == "android" and UserAgentOS == "linux") | summarize count(), arg_min(TimeGenerated,*) by DeviceOS, UserAgentOS, UserPrincipalName

Exclusions

Top-level NOT(...) conjuncts: predicates this rule actively suppresses.

Field	Kind	Excluded values
`UserAgent`	is_null	(no value, null check)
`AppId`	is_null	(no value, null check)
`DeviceOS`	is_null	(no value, null check)
`UserAgentOS`	eq	`unknown`
`DeviceOS`	contains	`UserAgentOS`
`UserAgentOS`	contains	`DeviceOS`
`DeviceOS`	eq	`ios`
`UserAgentOS`	eq	`macos`
`DeviceOS`	eq	`android`
`UserAgentOS`	eq	`linux`

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
`ResultType`	eq	`0` 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
`DeviceOS`	`summarize`
`UserAgentOS`	`summarize`
`UserPrincipalName`	`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)

Microsoft Entra ID UserAgent OS Missmatch

MITRE ATT&CK coverage

Rules detecting the same action

Rule body kusto

Stages and Predicates

Parameters

Let binding: `ExtractOSFromUA`

union `withsource=tbl_name` (2 sources)

Leg 1: `AADNonInteractiveUserSignInLogs`

Leg 2: `SigninLogs`

Applied to the combined result

Exclusions

Indicators

Output fields

Keyboard shortcuts

Search operators

Microsoft Entra ID UserAgent OS Missmatch

MITRE ATT&CK coverage

Rules detecting the same action

Rule body kusto

Stages and Predicates

Parameters

Let binding: ExtractOSFromUA

union withsource=tbl_name (2 sources)

Leg 1: AADNonInteractiveUserSignInLogs

Leg 2: SigninLogs

Applied to the combined result

Exclusions

Indicators

Output fields

Let binding: `ExtractOSFromUA`

union `withsource=tbl_name` (2 sources)

Leg 1: `AADNonInteractiveUserSignInLogs`

Leg 2: `SigninLogs`