Gmail Potential Spoofed Email Delivered

Severity: high
Entities: ip_addresses
Log types: GSuite.ActivityEvent
Tags: GSuite, Gmail, Email Security, Spoofing, Phishing
Reference: https://support.google.com/a/answer/12384955
Source: github.com/panther-labs/panther-analysis

Detects when a potentially spoofed email was successfully delivered to a user's inbox despite failing email authentication checks. This rule triggers when: 1. DMARC authentication fails, OR 2. Both SPF and DKIM authentication fail simultaneously These authentication failures indicate the sender may be impersonating a legitimate domain, which is a common tactic in phishing and business email compromise (BEC) attacks.

MITRE ATT&CK coverage

Tactic	Techniques
Initial Access	`T1566.001` Phishing: Spearphishing Attachment, `T1566.002` Phishing: Spearphishing Link

Rule body yaml

AnalysisType: rule
Filename: gsuite_potential_spoofed_email.py
RuleID: "GSuite.Gmail.Potential.Spoofed.Email"
DisplayName: "Gmail Potential Spoofed Email Delivered"
Enabled: true
LogTypes:
  - GSuite.ActivityEvent
Tags:
  - GSuite
  - Gmail
  - Email Security
  - Spoofing
  - Phishing
Reports:
  MITRE ATT&CK:
    - TA0001:T1566.001 # Initial Access: Phishing - Spearphishing Attachment
    - TA0001:T1566.002 # Initial Access: Phishing - Spearphishing Link
Severity: High
Description: >
  Detects when a potentially spoofed email was successfully delivered to a user's inbox despite
  failing email authentication checks. This rule triggers when:

  1. DMARC authentication fails, OR
  2. Both SPF and DKIM authentication fail simultaneously

  These authentication failures indicate the sender may be impersonating a legitimate domain,
  which is a common tactic in phishing and business email compromise (BEC) attacks.
Reference: https://support.google.com/a/answer/12384955
Runbook: |
  1. Review the sender's email address and compare with the From: header display name
  2. Check if the sender domain is impersonating an internal or partner domain
  3. Verify the authentication status details (SPF, DKIM, DMARC)
  4. Review the message subject and content if available
  5. Check the sender's IP geolocation and reputation
  6. Search for similar messages from the same sender to other users
  7. If confirmed as spoofing:
     - Add sender domain/IP to blocklist
     - Remove the message from user's inbox
     - Notify affected users not to interact with the email
  8. Consider strengthening DMARC policy (quarantine/reject) if not already enforced
DedupPeriodMinutes: 60
SummaryAttributes:
  - user_email
  - sender_address
  - dmarc_pass
  - spf_pass
  - dkim_pass
Tests:
  - Name: DMARC Failed - Successfully Delivered
    ExpectedResult: true
    Log:
      {
        "p_any_ip_addresses": ["8.8.8.8"],
        "p_event_time": "2025-11-05 10:15:30.000000000",
        "p_log_type": "GSuite.ActivityEvent",
        "actor": {
          "callerType": "USER",
          "email": "frodo@lotr.com",
          "profileId": "123456789"
        },
        "id": {
          "applicationName": "gmail",
          "customerId": "C01abc123",
          "time": "2025-11-05 10:15:30.000000000",
          "uniqueQualifier": "-123456789"
        },
        "ipAddress": "8.8.8.8",
        "kind": "admin#reports#activity",
        "name": "delivery",
        "parameters": {
          "event_info": {
            "elapsed_time_usec": 250000,
            "timestamp_usec": 1730800530000000,
            "success": true
          },
          "message_info": {
            "action_type": 2,
            "source": {
              "address": "john@justice.org",
              "from_header_address": "john@justice.org",
              "from_header_displayname": "CEO John Smith"
            },
            "destination": [
              {
                "address": "frodo@lotr.com",
                "service": "gmail-ui"
              }
            ],
            "connection_info": {
              "client_ip": "8.8.8.8",
              "is_internal": false,
              "dkim_pass": true,
              "spf_pass": true,
              "dmarc_pass": false,
              "dmarc_published_domain": "fake-company.com",
              "ip_geo_country": "RU"
            },
            "subject": "Urgent: Wire Transfer Request",
            "rfc2822_message_id": "<denethor@lotr.com>"
          }
        },
        "type": "message_delivery"
      }
  - Name: Both SPF and DKIM Failed - Successfully Delivered
    ExpectedResult: true
    Log:
      {
        "p_any_ip_addresses": ["7.7.7.7"],
        "p_event_time": "2025-11-05 11:30:00.000000000",
        "p_log_type": "GSuite.ActivityEvent",
        "actor": {
          "callerType": "USER",
          "email": "legolas@lotr.com",
          "profileId": "987654321"
        },
        "id": {
          "applicationName": "gmail",
          "customerId": "C01abc123",
          "time": "2025-11-05 11:30:00.000000000",
          "uniqueQualifier": "-987654321"
        },
        "ipAddress": "7.7.7.7",
        "kind": "admin#reports#activity",
        "name": "delivery",
        "parameters": {
          "event_info": {
            "elapsed_time_usec": 180000,
            "timestamp_usec": 1730804980000000,
            "success": true
          },
          "message_info": {
            "action_type": 2,
            "source": {
              "address": "eve@lexcorp.com",
              "from_header_address": "eve@lexcorp.com",
              "from_header_displayname": "PayPal Support"
            },
            "destination": [
              {
                "address": "legolas@lotr.com",
                "service": "gmail-ui"
              }
            ],
            "connection_info": {
              "client_ip": "7.7.7.7",
              "is_internal": false,
              "dkim_pass": false,
              "spf_pass": false,
              "dmarc_pass": true,
              "ip_geo_country": "CN"
            },
            "subject": "Your account has been suspended",
            "rfc2822_message_id": "<john@justice.org>"
          }
        },
        "type": "message_delivery"
      }
  - Name: All Authentication Failed - Successfully Delivered
    ExpectedResult: true
    Log:
      {
        "p_any_ip_addresses": ["6.6.6.6"],
        "p_event_time": "2025-11-05 12:00:00.000000000",
        "p_log_type": "GSuite.ActivityEvent",
        "actor": {
          "callerType": "USER",
          "email": "boromir@lotr.com",
          "profileId": "111222333"
        },
        "id": {
          "applicationName": "gmail",
          "customerId": "C01abc123",
          "time": "2025-11-05 12:00:00.000000000",
          "uniqueQualifier": "-111222333"
        },
        "ipAddress": "6.6.6.6",
        "kind": "admin#reports#activity",
        "name": "delivery",
        "parameters": {
          "event_info": {
            "elapsed_time_usec": 200000,
            "timestamp_usec": 1730806800000000,
            "success": true
          },
          "message_info": {
            "action_type": 2,
            "source": {
              "address": "denethor@lotr.com",
              "from_header_address": "denethor@lotr.com",
              "from_header_displayname": "Microsoft Billing"
            },
            "destination": [
              {
                "address": "boromir@lotr.com",
                "service": "gmail-ui"
              }
            ],
            "connection_info": {
              "client_ip": "6.6.6.6",
              "is_internal": false,
              "dkim_pass": false,
              "spf_pass": false,
              "dmarc_pass": false,
              "ip_geo_country": "VN"
            },
            "subject": "Invoice Past Due - Immediate Action Required",
            "rfc2822_message_id": "<eve@lexcorp.com>"
          }
        },
        "type": "message_delivery"
      }
  - Name: Only SPF Failed - Should Not Alert (One Factor Pass)
    ExpectedResult: false
    Log:
      {
        "p_any_ip_addresses": ["5.5.5.5"],
        "p_event_time": "2025-11-05 13:00:00.000000000",
        "p_log_type": "GSuite.ActivityEvent",
        "actor": {
          "callerType": "USER",
          "email": "denethor@lotr.com",
          "profileId": "444555666"
        },
        "id": {
          "applicationName": "gmail",
          "customerId": "C01abc123",
          "time": "2025-11-05 13:00:00.000000000",
          "uniqueQualifier": "-444555666"
        },
        "ipAddress": "5.5.5.5",
        "kind": "admin#reports#activity",
        "name": "delivery",
        "parameters": {
          "event_info": {
            "elapsed_time_usec": 150000,
            "timestamp_usec": 1730810400000000,
            "success": true
          },
          "message_info": {
            "action_type": 2,
            "source": {
              "address": "bruce@justice.org",
              "from_header_address": "bruce@justice.org"
            },
            "destination": [
              {
                "address": "denethor@lotr.com",
                "service": "gmail-ui"
              }
            ],
            "connection_info": {
              "client_ip": "5.5.5.5",
              "is_internal": false,
              "dkim_pass": true,
              "spf_pass": false,
              "dmarc_pass": true,
              "ip_geo_country": "US"
            },
            "subject": "Monthly Newsletter",
            "rfc2822_message_id": "<john@justice.org>"
          }
        },
        "type": "message_delivery"
      }
  - Name: All Authentication Passed - Should Not Alert
    ExpectedResult: false
    Log:
      {
        "p_any_ip_addresses": ["4.4.4.4"],
        "p_event_time": "2025-11-05 14:00:00.000000000",
        "p_log_type": "GSuite.ActivityEvent",
        "actor": {
          "callerType": "USER",
          "email": "legolas@lotr.com",
          "profileId": "777888999"
        },
        "id": {
          "applicationName": "gmail",
          "customerId": "C01abc123",
          "time": "2025-11-05 14:00:00.000000000",
          "uniqueQualifier": "-777888999"
        },
        "ipAddress": "4.4.4.4",
        "kind": "admin#reports#activity",
        "name": "delivery",
        "parameters": {
          "event_info": {
            "elapsed_time_usec": 100000,
            "timestamp_usec": 1730814000000000,
            "success": true
          },
          "message_info": {
            "action_type": 2,
            "source": {
              "address": "gandalf@lotr.com",
              "from_header_address": "gandalf@lotr.com",
              "from_header_displayname": "Jane Doe"
            },
            "destination": [
              {
                "address": "legolas@lotr.com",
                "service": "gmail-ui"
              }
            ],
            "connection_info": {
              "client_ip": "4.4.4.4",
              "is_internal": true,
              "is_intra_domain": true,
              "dkim_pass": true,
              "spf_pass": true,
              "dmarc_pass": true,
              "ip_geo_country": "US"
            },
            "subject": "Project Update",
            "rfc2822_message_id": "<gimli@lotr.com>"
          }
        },
        "type": "message_delivery"
      }
  - Name: Authentication Failed But Message Blocked - Should Not Alert
    ExpectedResult: false
    Log:
      {
        "p_any_ip_addresses": ["3.3.3.3"],
        "p_event_time": "2025-11-05 15:00:00.000000000",
        "p_log_type": "GSuite.ActivityEvent",
        "actor": {
          "callerType": "USER",
          "email": "boromir@lotr.com",
          "profileId": "222333444"
        },
        "id": {
          "applicationName": "gmail",
          "customerId": "C01abc123",
          "time": "2025-11-05 15:00:00.000000000",
          "uniqueQualifier": "-222333444"
        },
        "ipAddress": "3.3.3.3",
        "kind": "admin#reports#activity",
        "name": "delivery",
        "parameters": {
          "event_info": {
            "elapsed_time_usec": 120000,
            "timestamp_usec": 1730817600000000,
            "success": false
          },
          "message_info": {
            "action_type": 18,
            "source": {
              "address": "frodo@lotr.com",
              "from_header_address": "frodo@lotr.com"
            },
            "destination": [
              {
                "address": "boromir@lotr.com",
                "service": "gmail-ui"
              }
            ],
            "connection_info": {
              "client_ip": "3.3.3.3",
              "is_internal": false,
              "dkim_pass": false,
              "spf_pass": false,
              "dmarc_pass": false,
              "smtp_reply_code": 550,
              "smtp_response_reason": 4,
              "ip_geo_country": "XX"
            },
            "subject": "Spoofing Attempt",
            "rfc2822_message_id": "<denethor@lotr.com>"
          }
        },
        "type": "message_delivery"
      }
  - Name: Non-Gmail Event - Should Not Alert
    ExpectedResult: false
    Log:
      {
        "p_event_time": "2025-11-05 16:00:00.000000000",
        "p_log_type": "GSuite.ActivityEvent",
        "actor": {
          "callerType": "USER",
          "email": "denethor@lotr.com",
          "profileId": "555666777"
        },
        "id": {
          "applicationName": "drive",
          "customerId": "C01abc123",
          "time": "2025-11-05 16:00:00.000000000",
          "uniqueQualifier": "-555666777"
        },
        "ipAddress": "2.2.2.2",
        "kind": "admin#reports#activity",
        "name": "create",
        "type": "access"
      }
  - Name: Only DKIM Failed - Should Not Alert (Two Factors Pass)
    ExpectedResult: false
    Log:
      {
        "p_any_ip_addresses": ["172.16.0.30"],
        "p_event_time": "2025-11-05 17:00:00.000000000",
        "p_log_type": "GSuite.ActivityEvent",
        "actor": {
          "callerType": "USER",
          "email": "saruman@lotr.com",
          "profileId": "333444555"
        },
        "id": {
          "applicationName": "gmail",
          "customerId": "C01abc123",
          "time": "2025-11-05 17:00:00.000000000",
          "uniqueQualifier": "-333444555"
        },
        "ipAddress": "172.16.0.30",
        "kind": "admin#reports#activity",
        "name": "delivery",
        "parameters": {
          "event_info": {
            "elapsed_time_usec": 170000,
            "timestamp_usec": 1730825200000000,
            "success": true
          },
          "message_info": {
            "action_type": 2,
            "source": {
              "address": "vendor@supplier.com",
              "from_header_address": "vendor@supplier.com"
            },
            "destination": [
              {
                "address": "saruman@lotr.com",
                "service": "gmail-ui"
              }
            ],
            "connection_info": {
              "client_ip": "172.16.0.30",
              "is_internal": false,
              "dkim_pass": false,
              "spf_pass": true,
              "dmarc_pass": true,
              "ip_geo_country": "US"
            },
            "subject": "Purchase Order Confirmation",
            "rfc2822_message_id": "<po12345@supplier.com>"
          }
        },
        "type": "message_delivery"
      }

Detection logic

Condition

id.applicationName eq "gmail"
parameters.event_info.success eq "True"
parameters.message_info.connection_info.dmarc_pass eq "False" or (parameters.message_info.connection_info.spf_pass eq "False" and parameters.message_info.connection_info.dkim_pass eq "False")

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
`id.applicationName`	eq	`gmail`
`parameters.event_info.success`	eq	`True`
`parameters.message_info.connection_info.dkim_pass`	eq	`False`
`parameters.message_info.connection_info.dmarc_pass`	eq	`False`
`parameters.message_info.connection_info.spf_pass`	eq	`False`

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
`actor`	`actor.email`
`applicationName`	`id.applicationName`
`name`
`type`
`parameters`

`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)