Okta Sign-In from VPN Anonymizer

Severity: medium
Log types: Okta.SystemLog
Reference: https://sec.okta.com/articles/2023/08/cross-tenant-impersonation-prevention-and-detection
Source: github.com/panther-labs/panther-analysis

A user is attempting to sign-in to Okta from a known VPN anonymizer. The threat actor would access the compromised account using anonymizing proxy services.

MITRE ATT&CK coverage

Tactic	Techniques
Credential Access	`T1556` Modify Authentication Process

Rules detecting the same action

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

Failed Logins from Unknown or Invalid User (Kusto)
First Occurrence of Okta User Session Started via Proxy (Elastic)
High-Risk Admin Activity (Kusto)
Multiple Okta Sessions Detected for a Single User (Elastic)
Multiple Okta User Authentication Events with Same Device Token Hash (Elastic)
New Device/Location sign-in along with critical operation (Kusto)
Okta AiTM Session Cookie Replay (Elastic)
Okta Login Signal (Panther)

Rule body yaml

AnalysisType: rule
Filename: okta_anonymizing_vpn_login.py
RuleID: "Okta.Anonymizing.VPN.Login"
DisplayName: "Okta Sign-In from VPN Anonymizer"
Enabled: true
LogTypes:
  - Okta.SystemLog
Reports:
  MITRE ATT&CK:
    - TA0006:T1556 # Modify Authentication Process
Severity: Medium
Description: >
  A user is attempting to sign-in to Okta from a known VPN anonymizer.  The threat actor would access the compromised account using anonymizing proxy services.
Runbook: >
  Restrict this access to trusted Network Zones and deny access from anonymizing proxies in policy using a Dynamic Network Zone.
Reference: >
  https://sec.okta.com/articles/2023/08/cross-tenant-impersonation-prevention-and-detection
DedupPeriodMinutes: 360 # 6 hours
Threshold: 1
Tests:
  - Name: Other Event
    ExpectedResult: false
    Log:
      actor:
        alternateId: homer.simpson@duff.com
        displayName: Homer Simpson
        id: 00abc123
        type: User
      authenticationcontext:
        authenticationStep: 0
        externalSessionId: 100-abc-9999
      client:
        device: Computer
        geographicalContext:
          city: Springfield
          country: United States
          geolocation:
            lat: 20
            lon: -25
          postalCode: "12345"
          state: Ohio
        ipAddress: 1.3.2.4
        userAgent:
          browser: CHROME
          os: Mac OS X
          rawUserAgent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/102.0.0.0 Safari/537.36
        zone: "null"
      debugcontext:
        debugData:
          requestId: AbCdEf12G
          requestUri: /api/v1/users/AbCdEfG/lifecycle/reset_factors
          url: /api/v1/users/AbCdEfG/lifecycle/reset_factors?
      displaymessage: Authentication of user via MFA
      eventtype: user.session.start
      legacyeventtype: core.user.factor.attempt_fail
      outcome:
        reason: INVALID_CREDENTIALS
        result: FAILURE
      published: "2022-06-22 18:18:29.015"
      request:
        ipChain:
          - geographicalContext:
              city: Springfield
              country: United States
              geolocation:
                lat: 20
                lon: -25
              postalCode: "12345"
              state: Ohio
            ip: 1.3.2.4
            version: V4
      securitycontext:
        asNumber: 701
        asOrg: verizon
        domain: verizon.net
        isProxy: false
        isp: verizon
      severity: INFO
      target:
        - alternateId: peter.griffin@company.com
          displayName: Peter Griffin
          id: 0002222AAAA
          type: User
      transaction:
        detail: {}
        id: ABcDeFgG
        type: WEB
      uuid: AbC-123-XyZ
      version: "0"
  - Name: Anonymizing Proxy Used
    ExpectedResult: true
    Log:
      actor:
        alternateId: homer.simpson@duff.com
        displayName: Homer Simpson
        id: 00abc123
        type: User
      authenticationcontext:
        authenticationStep: 0
        externalSessionId: 100-abc-9999
      client:
        device: Computer
        geographicalContext:
          city: Springfield
          country: United States
          geolocation:
            lat: 20
            lon: -25
          postalCode: "12345"
          state: Ohio
        ipAddress: 1.3.2.4
        userAgent:
          browser: CHROME
          os: Mac OS X
          rawUserAgent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/102.0.0.0 Safari/537.36
        zone: "null"
      debugcontext:
        debugData:
          requestId: AbCdEf12G
          requestUri: /api/v1/users/AbCdEfG/lifecycle/reset_factors
          url: /api/v1/users/AbCdEfG/lifecycle/reset_factors?
      displaymessage: Authentication of user via MFA
      eventtype: user.session.start
      legacyeventtype: core.user.factor.attempt_fail
      outcome:
        reason: FastPass declined phishing attempt
        result: FAILURE
      published: "2022-06-22 18:18:29.015"
      request:
        ipChain:
          - geographicalContext:
              city: Springfield
              country: United States
              geolocation:
                lat: 20
                lon: -25
              postalCode: "12345"
              state: Ohio
            ip: 1.3.2.4
            version: V4
      securitycontext:
        asNumber: 701
        asOrg: verizon
        domain: anonymous.org
        isProxy: true
        isp: verizon
      severity: INFO
      target:
        - alternateId: peter.griffin@company.com
          displayName: Peter Griffin
          id: 0002222AAAA
          type: User
      transaction:
        detail: {}
        id: ABcDeFgG
        type: WEB
      uuid: AbC-123-XyZ
      version: "0"
  - Name: Apple Private Relay Used
    ExpectedResult: true
    Log:
      actor:
        alternateId: homer.simpson@duff.com
        displayName: Homer Simpson
        id: 00abc123
        type: User
      authenticationcontext:
        authenticationStep: 0
        externalSessionId: 100-abc-9999
      client:
        device: Computer
        geographicalContext:
          city: Springfield
          country: United States
          geolocation:
            lat: 20
            lon: -25
          postalCode: "12345"
          state: Ohio
        ipAddress: 1.3.2.4
        userAgent:
          browser: CHROME
          os: Mac OS X
          rawUserAgent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/102.0.0.0 Safari/537.36
        zone: "null"
      debugcontext:
        debugData:
          requestId: AbCdEf12G
          requestUri: /api/v1/users/AbCdEfG/lifecycle/reset_factors
          url: /api/v1/users/AbCdEfG/lifecycle/reset_factors?
      displaymessage: Authentication of user via MFA
      eventtype: user.session.start
      legacyeventtype: core.user.factor.attempt_fail
      outcome:
        reason: FastPass declined phishing attempt
        result: FAILURE
      p_enrichment:
        ipinfo_privacy:
          client.ipAddress:
            hosting: true
            p_match: 1.2.3.4
            proxy: false
            relay: true
            service: Apple Private Relay
            tor: false
            vpn: false
      published: "2022-06-22 18:18:29.015"
      request:
        ipChain:
          - geographicalContext:
              city: Springfield
              country: United States
              geolocation:
                lat: 20
                lon: -25
              postalCode: "12345"
              state: Ohio
            ip: 1.3.2.4
            version: V4
      securitycontext:
        asNumber: 701
        asOrg: verizon
        domain: anonymous.org
        isProxy: true
        isp: verizon
      severity: INFO
      target:
        - alternateId: peter.griffin@company.com
          displayName: Peter Griffin
          id: 0002222AAAA
          type: User
      transaction:
        detail: {}
        id: ABcDeFgG
        type: WEB
      uuid: AbC-123-XyZ
      version: "0"

Detection logic

Condition

eventType eq "user.session.start"
securityContext.isProxy is_not_null

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
`eventType`	eq	`user.session.start`
`securityContext.isProxy`	is_not_null	(no value, null check)

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
`event_type`	`eventtype`
`severity`
`actor`
`client`
`request`
`outcome`
`target`
`debug_context`	`debugcontext`
`authentication_context`	`authenticationcontext`
`security_context`	`securitycontext`
`ips`	`p_any_ip_addresses`
`displayName`	`actor.displayName`
`alternateId`	`actor.alternateId`

`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)