GCP VPC Flow Logs Disabled

Severity: medium
Entities: ip_addresses
Log types: GCP.AuditLog
Reference: https://cloud.google.com/vpc/docs/using-flow-logs
Source: github.com/panther-labs/panther-analysis

VPC flow logs were disabled for a subnet.

Rule body yaml

AnalysisType: rule
Description: VPC flow logs were disabled for a subnet.
DisplayName: "GCP VPC Flow Logs Disabled"
Enabled: true
Filename: gcp_vpc_flow_logs_disabled.py
Reference: https://cloud.google.com/vpc/docs/using-flow-logs
Severity: Medium
Tests:
  - ExpectedResult: true
    Log:
      insertId: "123456"
      logName: projects/gcp-project/logs/cloudaudit.googleapis.com%2Factivity
      operation:
        first: true
        id: operation-abc-123
        last: true
        producer: compute.googleapis.com
      p_any_ip_addresses:
        - 1.2.3.4
      p_event_time: "2023-03-08 18:52:58.322"
      p_log_type: GCP.AuditLog
      p_parse_time: "2023-03-08 18:54:14.597"
      p_source_label: gcplogsource
      protoPayload:
        at_sign_type: type.googleapis.com/google.cloud.audit.AuditLog
        authenticationInfo:
          principalEmail: user1@company.io
        authorizationInfo:
          - granted: true
            permission: compute.subnetworks.update
            resourceAttributes:
              name: projects/gcp-project/regions/us-central1/subnetworks/default
              service: compute
              type: compute.subnetworks
        methodName: v1.compute.subnetworks.patch
        request:
          "@type": type.googleapis.com/compute.subnetworks.patch
          enableFlowLogs: false
          fingerprint: "/�/��\x03��"
        requestMetadata:
          callerIP: 1.2.3.4
          callerSuppliedUserAgent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/110.0.0.0 Safari/537.36,gzip(gfe),gzip(gfe)
          destinationAttributes: {}
          requestAttributes:
            auth: {}
            reason: 8uSywAYQGg5Db2xpc2V1bSBGbG93cw
            time: "2023-03-08T18:52:58.731721Z"
        resourceName: projects/gcp-project/regions/us-central1/subnetworks/default
        response:
          "@type": type.googleapis.com/operation
          endTime: "2023-03-08T10:52:58.700-08:00"
          id: "123456"
          insertTime: "2023-03-08T10:52:58.699-08:00"
          name: operation-1678301578299-5f668096688bc-0635b6ef-4d0122bb
          operationType: compute.subnetworks.patch
          progress: "100"
          region: https://www.googleapis.com/compute/v1/projects/gcp-project/regions/us-central1
          selfLink: https://www.googleapis.com/compute/v1/projects/gcp-project/regions/us-central1/operations/1234
          selfLinkWithId: https://www.googleapis.com/compute/v1/projects/gcp-project/regions/us-central1/operations/1234
          startTime: "2023-03-08T10:52:58.700-08:00"
          status: DONE
          targetId: "123456"
          targetLink: https://www.googleapis.com/compute/v1/projects/gcp-project/regions/us-central1/subnetworks/default
          user: user1@company.io
        serviceName: compute.googleapis.com
      receiveTimestamp: "2023-03-08 18:52:58.991"
      resource:
        labels:
          location: us-central1
          project_id: gcp-project
          subnetwork_id: "123456"
          subnetwork_name: default
        type: gce_subnetwork
      severity: NOTICE
      timestamp: "2023-03-08 18:52:58.322"
    Name: Disable Flow Logs Event
  - ExpectedResult: false
    Log:
      insertId: "12345"
      logName: projects/test-project/logs/cloudaudit.googleapis.com%2Factivity
      operation:
        first: true
        id: operation-abcdefg-1234567
        last: true
        producer: compute.googleapis.com
      p_any_ip_addresses:
        - 1.2.3.4
      p_event_time: "2023-03-08 18:52:52.114"
      p_log_type: GCP.AuditLog
      p_parse_time: "2023-03-08 18:54:14.595"
      p_row_id: 5e7586fcbb73fdeed985ebeb16bd0c
      p_source_id: 4fc88a5a-2d51-4279-9c4a-08fa7cc52566
      p_source_label: gcplogsource
      protoPayload:
        at_sign_type: type.googleapis.com/google.cloud.audit.AuditLog
        authenticationInfo:
          principalEmail: user1@company.io
        authorizationInfo:
          - granted: true
            permission: compute.subnetworks.update
            resourceAttributes:
              name: projects/test-project/regions/us-central1/subnetworks/default
              service: compute
              type: compute.subnetworks
        methodName: v1.compute.subnetworks.patch
        request:
          "@type": type.googleapis.com/compute.subnetworks.patch
          fingerprint: "/�/��\x03��"
          logConfig:
            enable: true
        requestMetadata:
          callerIP: 1.2.3.4
          callerSuppliedUserAgent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/110.0.0.0 Safari/537.36,gzip(gfe),gzip(gfe)
          destinationAttributes: {}
          requestAttributes:
            auth: {}
            reason: 8uSywAYQGg5Db2xpc2V1bSBGbG93cw
            time: "2023-03-08T18:52:52.558899Z"
        resourceName: projects/test-project/regions/us-central1/subnetworks/default
        response:
          "@type": type.googleapis.com/operation
          endTime: "2023-03-08T10:52:52.510-08:00"
          id: "9876543210"
          insertTime: "2023-03-08T10:52:52.509-08:00"
          name: operation-abcdefg-1234567
          operationType: compute.subnetworks.patch
          progress: "100"
          region: https://www.googleapis.com/compute/v1/projects/test-project/regions/us-central1
          selfLink: https://www.googleapis.com/compute/v1/projects/test-project/regions/us-central1/operations/operation-abcdefg-1234567
          selfLinkWithId: https://www.googleapis.com/compute/v1/projects/test-project/regions/us-central1/operations/9876543210
          startTime: "2023-03-08T10:52:52.510-08:00"
          status: DONE
          targetId: "567854321"
          targetLink: https://www.googleapis.com/compute/v1/projects/test-project/regions/us-central1/subnetworks/default
          user: user1@company.io
        serviceName: compute.googleapis.com
      receiveTimestamp: "2023-03-08 18:52:52.72"
      resource:
        labels:
          location: us-central1
          project_id: test-project
          subnetwork_id: "567854321"
          subnetwork_name: default
        type: gce_subnetwork
      severity: NOTICE
      timestamp: "2023-03-08 18:52:52.114"
    Name: Enable Flow Logs Event
DedupPeriodMinutes: 60
LogTypes:
  - GCP.AuditLog
RuleID: "GCP.VPC.Flow.Logs.Disabled"
Threshold: 1

Detection logic

Condition

protoPayload is_not_null
protoPayload.methodName eq "v1.compute.subnetworks.patch"
protoPayload.request.enableFlowLogs 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
`protoPayload`	is_not_null	(no value, null check)
`protoPayload.methodName`	eq	`v1.compute.subnetworks.patch`
`protoPayload.request.enableFlowLogs`	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
`principalEmail`	`protoPayload.authenticationInfo.principalEmail`
`resourceName`	`protoPayload.resourceName`

`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)