Hunt for suspicious sign-in to Entra ID Using Extrnal Call Method

Severity: medium
Type: hunt
Time window: 5m
Match by: ip, user
Author: Google Cloud Security
Source: github.com/chronicle/detection-rules

Detects authentication to O365 followed by a non-interactive sign-ins that aligns to suspicious activity.

References

https://github.com/dafthack/GraphRunner/blob/main/GraphRunner.ps1

Event coverage

Provider	Event
M365-AzureActiveDirectory	UserLoggedIn

Rules detecting the same action

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

Azure Login Bypassing Conditional Access Policies (Sigma)
M365 Identity OAuth Flow by First-Party Microsoft App from Multiple IPs (Elastic)
M365 Identity OAuth Flow by User Sign-in to Device Registration (Elastic)
M365 Identity OAuth Phishing via First-Party Microsoft Application (Elastic)
M365 Potential AiTM UserLoggedIn via Office App (Tycoon2FA) (Elastic)
O365 AD PowerShell App Login Subsequent Activity (YARA-L)
O365 Admin Login Activity To Uncommon Microsoft Cloud Apps (YARA-L)
O365 Login Activity To Azure AD PowerShell App (YARA-L)

Rule body yaral

/*
 * Copyright 2025 Google LLC
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

rule suspicious_entra_id_sign_in_external_call {

  meta:
    author = "Google Cloud Security"
    description = "Detects authentication to O365 followed by a non-interactive sign-ins that aligns to suspicious activity."
    rule_id = "mr_2245edf0-3a75-4bf6-901b-c47ffda1703e"
    rule_name = "Hunt for suspicious sign-in to Entra ID Using Extrnal Call Method"
    assumption = "Microsoft Office is the application the stolen token is associated with, however this can be modified in GraphRunner. This detection could create FPs if not focusing on the default application, however filtering on suspicious IP addresses or user agents may help make this useful as a hunting rule."
    reference = "https://github.com/dafthack/GraphRunner/blob/main/GraphRunner.ps1"
    type = "hunt"
    platform = "azure"
    data_source = "o365, azure activity"
    severity = "Medium"
    priority = "Medium"

  events:
    $init_login.metadata.event_type = "USER_LOGIN"
    $init_login.metadata.product_event_type = "UserLoggedIn"
    $init_login.metadata.product_name = "Office 365"
    $init_login.metadata.vendor_name = "Microsoft"
    $init_login.security_result.action = "ALLOW"
    $init_login.network.session_id != ""
    strings.to_lower($init_login.target.user.userid) = $user
    $init_login.principal.ip = $ip
    //Can add specific IPs of interest here or filter admin consoles out
    //$init_login.principal.ip != "10.10.10.10"

    $init_login.network.session_id != $sub_login.network.session_id
    $init_login.target.application != $sub_login.target.application
    $init_login.network.http.user_agent != $sub_login.network.http.user_agent
    $init_login.metadata.event_timestamp.seconds < $sub_login.metadata.event_timestamp.seconds

    $sub_login.metadata.event_type = "USER_LOGIN"
    $sub_login.metadata.product_event_type = "Sign-in activity"
    $sub_login.metadata.product_name = "Azure Activity"
    $sub_login.metadata.vendor_name = "Microsoft"
    $sub_login.security_result.action = "ALLOW"
    $sub_login.security_result.category_details = "NonInteractiveUserSignInLogs"
    //Microsoft Office GUID is the default application used with Get-GraphTokens function. This can be customized but is a good place to start
    //$sub_login.target.application = "Microsoft Office"
    //UA listing displayed here as strings separated by or statement
    //Each line is commented with device or browser or combination as specified in GraphRunner
    //Could also convert to regex to refine if desired or used with a list
    (
        $sub_login.network.http.user_agent = "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_14_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/91.0.4472.114 Safari/537.36" nocase or // Mac/Chrome | Chrome
        $sub_login.network.http.user_agent = "Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:70.0) Gecko/20100101 Firefox/70.0" nocase or // Mac/Firefox
        $sub_login.network.http.user_agent = "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_14_6) AppleWebKit/605.1.15 (KHTML, like Gecko) Chrome/91.0.4472.114 Safari/604.1 Edg/91.0.100.0" nocase or // Mac/Edge
        $sub_login.network.http.user_agent = "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_14_6) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/13.0.3 Safari/605.1.15" nocase or // Mac/Safari | Mac | Safari
        $sub_login.network.http.user_agent = "Mozilla/5.0 (Windows NT 10.0; WOW64; Trident/7.0; rv:11.0) like Gecko" nocase or // Windows/IE | IE
        $sub_login.network.http.user_agent = "Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/91.0.4472.114 Safari/537.36" nocase or // Windows/Chrome
        $sub_login.network.http.user_agent = "Mozilla/5.0 (Windows NT 10.0; WOW64; rv:70.0) Gecko/20100101 Firefox/70.0" nocase or // Windows/Firefox | Firefox
        $sub_login.network.http.user_agent = "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/70.0.3538.102 Safari/537.36 Edge/18.19042" nocase or // Windows/Edge | Windows
        $sub_login.network.http.user_agent = "Mozilla/5.0 (Linux; U; Android 4.0.2; en-us; Galaxy Nexus Build/ICL53F) AppleWebKit/534.30 (KHTML, like Gecko) Version/4.0 Mobile Safari/534.30" nocase or // AndroidMobile/Android | AndroidMobile | Android
        $sub_login.network.http.user_agent = "Mozilla/5.0 (Linux; Android 6.0; Nexus 5 Build/MRA58N) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/91.0.4472.114 Mobile Safari/537.36" nocase or // AndroidMobile/Chrome
        $sub_login.network.http.user_agent = "Mozilla/5.0 (Android 4.4; Mobile; rv:70.0) Gecko/70.0 Firefox/70.0" nocase or // AndroidMobile/Firefox
        $sub_login.network.http.user_agent = "Mozilla/5.0 (Linux; Android 8.1.0; Pixel Build/OPM4.171019.021.D1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/65.0.3325.109 Mobile Safari/537.36 EdgA/42.0.0.2057" nocase or // AndroidMobile/Edge
        $sub_login.network.http.user_agent = "Mozilla/5.0 (iPhone; CPU iPhone OS 13_2 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) CriOS/91.0.4472.114 Mobile/15E148 Safari/604.1" nocase or // iPhone/Chrome
        $sub_login.network.http.user_agent = "Mozilla/5.0 (iPhone; CPU iPhone OS 8_3 like Mac OS X) AppleWebKit/600.1.4 (KHTML, like Gecko) FxiOS/1.0 Mobile/12F69 Safari/600.1.4" nocase or // iPhone/Firefox
        $sub_login.network.http.user_agent = "Mozilla/5.0 (iPhone; CPU iPhone OS 12_3_1 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/12.1.1 EdgiOS/44.5.0.10 Mobile/15E148 Safari/604.1" nocase or // iPhone/Edge
        $sub_login.network.http.user_agent = "Mozilla/5.0 (iPhone; CPU iPhone OS 13_2_3 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/13.0.3 Mobile/15E148 Safari/604.1" nocase or // iPhone/Safari | iPhone
        $sub_login.network.http.user_agent = "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/103.0.0.0 Safari/537.36" nocase // Edge
    )
    strings.to_lower($sub_login.principal.user.email_addresses[0]) = $user
    $sub_login.principal.ip = $ip

  match:
    $user, $ip over 5m

  outcome:
    $risk_score = 65
    $event_count = count_distinct($init_login.metadata.id)
    $init_user_agent = array_distinct($init_login.network.http.user_agent)
    $sub_user_agent = array_distinct($sub_login.network.http.user_agent)
    $security_summary = array_distinct($init_login.security_result.summary)
    $init_target_application = array_distinct($init_login.target.application)
    $sub_target_application = array_distinct($sub_login.target.application)
    //$principal_user_userid = array_distinct($group.principal.user.userid)
    $principal_user =array_distinct($user)
    $principal_ip = array_distinct($init_login.principal.ip)
    $session_id = array_distinct($init_login.network.session_id)

  condition:
    $init_login and $sub_login
}

Detection logic

Fires when at least one $init_login event in the 5m window and at least one $sub_login event in the 5m window.

Events

`$init_login` `USER_LOGIN`

metadata.product_event_type = "UserLoggedIn"
security_result.action = "ALLOW"
network.session_id is not null

`$strings.to_lower()`

No field filters (binds the event for correlation only).

`$sub_login` `USER_LOGIN`

metadata.product_event_type = "Sign-in activity"
security_result.action = "ALLOW"
security_result.category_details = "NonInteractiveUserSignInLogs"
network.http.user_agent = "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_14_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/91.0.4472.114 Safari/537.36" or "Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:70.0) Gecko/20100101 Firefox/70.0" or "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_14_6) AppleWebKit/605.1.15 (KHTML, like Gecko) Chrome/91.0.4472.114 Safari/604.1 Edg/91.0.100.0" or "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_14_6) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/13.0.3 Safari/605.1.15" or "Mozilla/5.0 (Windows NT 10.0; WOW64; Trident/7.0; rv:11.0) like Gecko" or "Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/91.0.4472.114 Safari/537.36" or "Mozilla/5.0 (Windows NT 10.0; WOW64; rv:70.0) Gecko/20100101 Firefox/70.0" or "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/70.0.3538.102 Safari/537.36 Edge/18.19042" or "Mozilla/5.0 (Linux; U; Android 4.0.2; en-us; Galaxy Nexus Build/ICL53F) AppleWebKit/534.30 (KHTML, like Gecko) Version/4.0 Mobile Safari/534.30" or "Mozilla/5.0 (Linux; Android 6.0; Nexus 5 Build/MRA58N) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/91.0.4472.114 Mobile Safari/537.36" or "Mozilla/5.0 (Android 4.4; Mobile; rv:70.0) Gecko/70.0 Firefox/70.0" or "Mozilla/5.0 (Linux; Android 8.1.0; Pixel Build/OPM4.171019.021.D1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/65.0.3325.109 Mobile Safari/537.36 EdgA/42.0.0.2057" or "Mozilla/5.0 (iPhone; CPU iPhone OS 13_2 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) CriOS/91.0.4472.114 Mobile/15E148 Safari/604.1" or "Mozilla/5.0 (iPhone; CPU iPhone OS 8_3 like Mac OS X) AppleWebKit/600.1.4 (KHTML, like Gecko) FxiOS/1.0 Mobile/12F69 Safari/600.1.4" or "Mozilla/5.0 (iPhone; CPU iPhone OS 12_3_1 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/12.1.1 EdgiOS/44.5.0.10 Mobile/15E148 Safari/604.1" or "Mozilla/5.0 (iPhone; CPU iPhone OS 13_2_3 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/13.0.3 Mobile/15E148 Safari/604.1" or "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/103.0.0.0 Safari/537.36"

Correlation

Joined on: $init_login.network.session_id != $sub_login.network.session_id
$init_login.target.application != $sub_login.target.application
$init_login.network.http.user_agent != $sub_login.network.http.user_agent
Order: $init_login before $sub_login
Match key: $ip (principal.ip), $user
Within: 5m

Outcome

Fields the detection emits on a match. $risk_score drives alerting; Chronicle surfaces the rest on the detection.

Field	Expression
`risk_score`	`65`
`event_count`	`count_distinct($init_login.metadata.id)`
`init_user_agent`	`array_distinct($init_login.network.http.user_agent)`
`sub_user_agent`	`array_distinct($sub_login.network.http.user_agent)`
`security_summary`	`array_distinct($init_login.security_result.summary)`
`init_target_application`	`array_distinct($init_login.target.application)`
`sub_target_application`	`array_distinct($sub_login.target.application)`
`principal_user`	`array_distinct($user)`
`principal_ip`	`array_distinct($init_login.principal.ip)`
`session_id`	`array_distinct($init_login.network.session_id)`

`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)

Hunt for suspicious sign-in to Entra ID Using Extrnal Call Method

References

Event coverage

Rules detecting the same action

Rule body yaral

Detection logic

Events

`$init_login` `USER_LOGIN`

`$strings.to_lower()`

`$sub_login` `USER_LOGIN`

Correlation

Outcome

Keyboard shortcuts

Search operators

Hunt for suspicious sign-in to Entra ID Using Extrnal Call Method

References

Event coverage

Rules detecting the same action

Rule body yaral

Detection logic

Events

$init_login USER_LOGIN

$strings.to_lower()

$sub_login USER_LOGIN

Correlation

Outcome

`$init_login` `USER_LOGIN`

`$strings.to_lower()`

`$sub_login` `USER_LOGIN`