GCP Service Account Access Denied

Severity: low
Log types: GCP.AuditLog
Tags: GCP, Service Account, Access
Reference: https://cloud.google.com/iam/docs/service-account-overview
Source: github.com/panther-labs/panther-analysis

This rule detects deletions of GCP Log Buckets or Sinks.

Rule body yaml

---
AnalysisType: rule
DedupPeriodMinutes: 5
Threshold: 30
DisplayName: GCP Service Account Access Denied
Enabled: true
Filename: gcp_service_account_access_denied.py
RuleID: "GCP.Service.Account.Access.Denied"
Severity: Low
LogTypes:
  - GCP.AuditLog
Tags:
  - GCP
  - Service Account
  - Access
Description: >
  This rule detects deletions of GCP Log Buckets or Sinks.
Runbook: >
  Ensure that the bucket or sink deletion was expected. Adversaries may do this to cover their tracks.
Reference: https://cloud.google.com/iam/docs/service-account-overview
Tests:
  - Name: service-account.access-denied-should-alert
    LogType: GCP.AuditLog
    ExpectedResult: true
    Log:
      {
        "insertid": "xxxxxxxxxxxx",
        "logname": "projects/test-project-123456/logs/cloudaudit.googleapis.com%2Factivity",
        "protoPayload":
          {
            "at_sign_type": "type.googleapis.com/google.cloud.audit.AuditLog",
            "authenticationInfo":
              {
                "principalEmail": "test-no-perms@test-project-123456.iam.gserviceaccount.com",
                "principalSubject": "serviceAccount:test-no-perms@test-project-123456.iam.gserviceaccount.com",
                "serviceAccountKeyName": "//iam.googleapis.com/projects/test-project-123456/serviceAccounts/test-no-perms@test-project-123456.iam.gserviceaccount.com/keys/a0064fe0ef82b9e256b8b093d927ee842a19da34",
              },
            "authorizationInfo":
              [
                {
                  "permission": "iam.serviceAccounts.create",
                  "resource": "projects/test-project-123456",
                  "resourceAttributes": {},
                },
              ],
            "methodName": "google.iam.admin.v1.CreateServiceAccount",
            "request":
              {
                "@type": "type.googleapis.com/google.iam.admin.v1.CreateServiceAccountRequest",
                "account_id": "test123",
                "name": "projects/test-project-123456",
                "service_account": {},
              },
            "requestMetadata":
              {
                "callerIP": "12.12.12.12",
                "callerSuppliedUserAgent": "google-cloud-sdk gcloud/431.0.0 command/gcloud.iam.service-accounts.create invocation-id/b2ea5dab8c9b4bff8bc15ab299dff79e environment/devshell environment-version/None client-os/LINUX client-os-ver/5.15.107 client-pltf-arch/x86_64 interactive/True from-script/False python/3.9.2 term/screen (Linux 5.15.107+),gzip(gfe)",
                "destinationAttributes": {},
                "requestAttributes":
                  { "auth": {}, "time": "2023-05-24T21:12:55.211301546Z" },
              },
            "resourceName": "projects/test-project-123456",
            "response":
              {
                "@type": "type.googleapis.com/google.iam.admin.v1.ServiceAccount",
              },
            "serviceName": "iam.googleapis.com",
            "status":
              {
                "code": 7,
                "details":
                  [
                    {
                      "@type": "type.googleapis.com/google.rpc.ErrorInfo",
                      "domain": "iam.googleapis.com",
                      "metadata":
                        { "permission": "iam.serviceAccounts.create" },
                      "reason": "IAM_PERMISSION_DENIED",
                    },
                  ],
                "message": "Permission 'iam.serviceAccounts.create' denied on resource (or it may not exist).",
              },
          },
        "receivetimestamp": "2023-05-24 21:12:55.964",
        "resource":
          {
            "labels":
              {
                "email_id": "",
                "project_id": "test-project-123456",
                "unique_id": "",
              },
            "type": "service_account",
          },
        "severity": "ERROR",
        "timestamp": "2023-05-24 21:12:55.145",
      }
  - Name: service-account.access-grated-should-not-alert
    LogType: GCP.AuditLog
    ExpectedResult: false
    Log:
      {
        "insertId": "xxxxxxxxxxxx",
        "logName": "projects/test-project-123456/logs/cloudaudit.googleapis.com%2Factivity",
        "protoPayload":
          {
            "at_sign_type": "type.googleapis.com/google.cloud.audit.AuditLog",
            "authenticationInfo": {},
            "authorizationInfo":
              [
                {
                  "granted": true,
                  "permission": "iam.serviceAccounts.create",
                  "resource": "projects/test-project-123456",
                  "resourceAttributes": {},
                },
              ],
            "methodName": "google.iam.admin.v1.CreateServiceAccount",
            "request":
              {
                "@type": "type.googleapis.com/google.iam.admin.v1.CreateServiceAccountRequest",
                "account_id": "appengine-default",
                "name": "projects/test-project-123456",
                "service_account":
                  {
                    "display_name": "App Engine default service account",
                    "email": "test-project-123456@appspot.gserviceaccount.com",
                  },
              },
            "requestMetadata":
              {
                "callerIP": "private",
                "destinationAttributes": {},
                "requestAttributes":
                  { "auth": {}, "time": "2023-05-23T19:27:42.510877536Z" },
              },
            "resourceName": "projects/test-project-123456",
            "response":
              {
                "@type": "type.googleapis.com/google.iam.admin.v1.ServiceAccount",
                "display_name": "App Engine default service account",
                "email": "test-project-123456@appspot.gserviceaccount.com",
                "etag": "MDEwMjE5MjA=",
                "name": "projects/test-project-123456/serviceAccounts/test-project-123456@appspot.gserviceaccount.com",
                "oauth2_client_id": "114240096070638624820",
                "project_id": "test-project-123456",
                "unique_id": "114240096070638624820",
              },
            "serviceName": "iam.googleapis.com",
            "status": { "message": "OK" },
          },
        "receiveTimestamp": "2023-05-23 19:27:44.037",
        "resource":
          {
            "labels":
              {
                "email_id": "test-project-123456@appspot.gserviceaccount.com",
                "project_id": "test-project-123456",
                "unique_id": "114240096070638624820",
              },
            "type": "service_account",
          },
        "severity": "NOTICE",
        "timestamp": "2023-05-23 19:27:42.492",
      }

Detection logic

Condition

protoPayload.status.details.reason eq "IAM_PERMISSION_DENIED"

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
`protoPayload.status.details.reason`	eq	`IAM_PERMISSION_DENIED`

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
`project`	`resource.labels.project_id`
`principal`	`protoPayload.authenticationInfo.principalEmail`
`caller_ip`	`protoPayload.requestMetadata.callerIP`
`methodName`	`protoPayload.methodName`
`resourceName`	`protoPayload.resourceName`
`serviceName`	`protoPayload.serviceName`

`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)