GCP Access Attempts Violating IAP Access Controls

Severity: medium
Entities: ip_addresses, trace_ids
Log types: GCP.HTTPLoadBalancer
Reference: https://cloud.google.com/iap/docs/concepts-overview
Source: github.com/panther-labs/panther-analysis

Rule body yaml

AnalysisType: rule
Description: GCP Access Attempts Violating IAP Access Controls
DisplayName: "GCP Access Attempts Violating IAP Access Controls"
Enabled: true
Filename: gcp_access_attempts_violating_iap_access_controls.py
Reference: https://cloud.google.com/iap/docs/concepts-overview
Severity: Medium
Tests:
  - ExpectedResult: true
    Log:
      httprequest:
        latency: 0.048180s
        remoteIp: 1.2.3.4
        requestMethod: GET
        requestSize: 77
        requestUrl: http://6.7.8.9/
        responseSize: 211
        status: 403
        userAgent: curl/7.85.0
      insertid: u94qwjf25yzns
      jsonpayload:
        at_sign_type: type.googleapis.com/google.cloud.loadbalancing.type.LoadBalancerLogEntry
        remoteIp: 1.2.3.4
        statusDetails: handled_by_identity_aware_proxy
      logname: projects/gcp-project1/logs/requests
      p_any_ip_addresses:
        - 6.7.8.9
        - 1.2.3.4
      p_any_trace_ids:
        - projects/gcp-project1/traces/dd43c6eb7046da54fa3724d2753262e6
      p_event_time: "2023-03-09 23:19:25.712"
      p_log_type: GCP.HTTPLoadBalancer
      p_parse_time: "2023-03-09 23:21:14.47"
      p_row_id: be93fccee09dd2f1b0b2d9ee16d5d704
      p_schema_version: 0
      p_source_id: 964c7894-9a0d-4ddf-864f-0193438221d6
      p_source_label: panther-gcp-logsource
      receivetimestamp: "2023-03-09 23:19:26.392"
      resource:
        labels:
          backend_service_name: web-backend-service
          forwarding_rule_name: http-content-rule
          project_id: gcp-project1
          target_proxy_name: http-lb-proxy-2
          url_map_name: web-map-http-2
          zone: global
        type: http_load_balancer
      severity: INFO
      spanid: d75cc31c93528953
      timestamp: "2023-03-09 23:19:25.712"
      trace: projects/gcp-project1/traces/dd43c6eb7046da54fa3724d2753262e6
    Name: Blocked By IAP
  - ExpectedResult: false
    Log:
      httprequest:
        latency: 0.048180s
        remoteIp: 1.2.3.4
        requestMethod: GET
        requestSize: 77
        requestUrl: http://6.7.8.9/
        responseSize: 211
        status: 302
        userAgent: curl/7.85.0
      insertid: u94qwjf25yzns
      jsonpayload:
        at_sign_type: type.googleapis.com/google.cloud.loadbalancing.type.LoadBalancerLogEntry
        remoteIp: 1.2.3.4
        statusDetails: handled_by_identity_aware_proxy
      logname: projects/gcp-project1/logs/requests
      p_any_ip_addresses:
        - 6.7.8.9
        - 1.2.3.4
      p_any_trace_ids:
        - projects/gcp-project1/traces/dd43c6eb7046da54fa3724d2753262e6
      p_event_time: "2023-03-09 23:19:25.712"
      p_log_type: GCP.HTTPLoadBalancer
      p_parse_time: "2023-03-09 23:21:14.47"
      p_row_id: be93fccee09dd2f1b0b2d9ee16d5d704
      p_schema_version: 0
      p_source_id: 964c7894-9a0d-4ddf-864f-0193438221d6
      p_source_label: panther-gcp-logsource
      receivetimestamp: "2023-03-09 23:19:26.392"
      resource:
        labels:
          backend_service_name: web-backend-service
          forwarding_rule_name: http-content-rule
          project_id: gcp-project1
          target_proxy_name: http-lb-proxy-2
          url_map_name: web-map-http-2
          zone: global
        type: http_load_balancer
      severity: INFO
      spanid: d75cc31c93528953
      timestamp: "2023-03-09 23:19:25.712"
      trace: projects/gcp-project1/traces/dd43c6eb7046da54fa3724d2753262e6
    Name: Redirected by IAP
DedupPeriodMinutes: 60
LogTypes:
  - GCP.HTTPLoadBalancer
RuleID: "GCP.Access.Attempts.Violating.IAP.Access.Controls"
Threshold: 1

Detection logic

Condition

resource.type eq "http_load_balancer"
jsonPayload.statusDetails eq "handled_by_identity_aware_proxy"
not (httprequest.status starts_with "2" or httprequest.status starts_with "3")

Exclusions

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

Field	Kind	Excluded values
`httprequest.status`	starts_with	`2`
`httprequest.status`	starts_with	`3`

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
`jsonPayload.statusDetails`	eq	`handled_by_identity_aware_proxy`
`resource.type`	eq	`http_load_balancer`

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
`remoteIp`	`jsonPayload.remoteIp`
`requestUrl`	`httprequest.requestUrl`

`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)

GCP Access Attempts Violating IAP Access Controls

Rule body yaml

Detection logic

Condition

Exclusions

Indicators

Output fields

Keyboard shortcuts

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