diff --git a/x-pack/test/security_solution_api_integration/test_suites/detections_response/rules_management/prebuilt_rules/prebuilt_rule_customization/customization_enabled/index.ts b/x-pack/test/security_solution_api_integration/test_suites/detections_response/rules_management/prebuilt_rules/prebuilt_rule_customization/customization_enabled/index.ts
index 0d811f57288ae..625b37ebd1300 100644
--- a/x-pack/test/security_solution_api_integration/test_suites/detections_response/rules_management/prebuilt_rules/prebuilt_rule_customization/customization_enabled/index.ts
+++ b/x-pack/test/security_solution_api_integration/test_suites/detections_response/rules_management/prebuilt_rules/prebuilt_rule_customization/customization_enabled/index.ts
@@ -12,6 +12,7 @@ export default ({ loadTestFile }: FtrProviderContext): void => {
     loadTestFile(require.resolve('./is_customized_calculation'));
     loadTestFile(require.resolve('./import_rules'));
     loadTestFile(require.resolve('./rules_export'));
+    loadTestFile(require.resolve('./rule_customization'));
     loadTestFile(require.resolve('./preview_prebuilt_rules_upgrade'));
     loadTestFile(require.resolve('./upgrade_prebuilt_rules'));
   });
diff --git a/x-pack/test/security_solution_api_integration/test_suites/detections_response/rules_management/prebuilt_rules/prebuilt_rule_customization/customization_enabled/rule_customization.ts b/x-pack/test/security_solution_api_integration/test_suites/detections_response/rules_management/prebuilt_rules/prebuilt_rule_customization/customization_enabled/rule_customization.ts
new file mode 100644
index 0000000000000..1baebc762e483
--- /dev/null
+++ b/x-pack/test/security_solution_api_integration/test_suites/detections_response/rules_management/prebuilt_rules/prebuilt_rule_customization/customization_enabled/rule_customization.ts
@@ -0,0 +1,924 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License
+ * 2.0; you may not use this file except in compliance with the Elastic License
+ * 2.0.
+ */
+import expect from 'expect';
+import {
+  getPrebuiltRuleMock,
+  getPrebuiltRuleMockOfType,
+} from '@kbn/security-solution-plugin/server/lib/detection_engine/prebuilt_rules/mocks';
+import { deleteAllRules } from '../../../../../../../common/utils/security_solution';
+import { FtrProviderContext } from '../../../../../../ftr_provider_context';
+import {
+  createPrebuiltRuleAssetSavedObjects,
+  createRuleAssetSavedObject,
+  deleteAllPrebuiltRuleAssets,
+  getWebHookAction,
+  installPrebuiltRules,
+} from '../../../../utils';
+
+export default ({ getService }: FtrProviderContext): void => {
+  const es = getService('es');
+  const supertest = getService('supertest');
+  const securitySolutionApi = getService('securitySolutionApi');
+  const log = getService('log');
+
+  const ruleAsset = createRuleAssetSavedObject({
+    rule_id: 'rule_1',
+  });
+
+  describe('@ess @serverless @skipInServerlessMKI rule customization', () => {
+    before(async () => {
+      await deleteAllRules(supertest, log);
+      await deleteAllPrebuiltRuleAssets(es, log);
+    });
+
+    describe('detecting rule customizations', () => {
+      describe('common rule fields', () => {
+        beforeEach(async () => {
+          await createPrebuiltRuleAssetSavedObjects(es, [ruleAsset]);
+          await installPrebuiltRules(es, supertest);
+        });
+
+        afterEach(async () => {
+          await deleteAllRules(supertest, log);
+          await deleteAllPrebuiltRuleAssets(es, log);
+        });
+
+        it('name field', async () => {
+          const { body } = await securitySolutionApi
+            .patchRule({ body: { rule_id: 'rule_1', name: 'some other name' } })
+            .expect(200);
+
+          expect(body.rule_source.is_customized).toEqual(true);
+          expect(body.rule_source.type).toEqual('external');
+        });
+
+        it('description field', async () => {
+          const { body } = await securitySolutionApi
+            .patchRule({ body: { rule_id: 'rule_1', description: 'some other description' } })
+            .expect(200);
+
+          expect(body.rule_source.is_customized).toEqual(true);
+          expect(body.rule_source.type).toEqual('external');
+        });
+
+        it('interval field', async () => {
+          const { body } = await securitySolutionApi
+            .patchRule({ body: { rule_id: 'rule_1', interval: '30m' } })
+            .expect(200);
+
+          expect(body.rule_source.is_customized).toEqual(true);
+          expect(body.rule_source.type).toEqual('external');
+        });
+
+        it('from field', async () => {
+          const { body } = await securitySolutionApi
+            .patchRule({ body: { rule_id: 'rule_1', from: 'now-10m' } })
+            .expect(200);
+
+          expect(body.rule_source.is_customized).toEqual(true);
+          expect(body.rule_source.type).toEqual('external');
+        });
+
+        it('to field', async () => {
+          const { body } = await securitySolutionApi
+            .patchRule({ body: { rule_id: 'rule_1', to: 'now-1m' } })
+            .expect(200);
+
+          expect(body.rule_source.is_customized).toEqual(true);
+          expect(body.rule_source.type).toEqual('external');
+        });
+
+        it('note field', async () => {
+          const { body } = await securitySolutionApi
+            .patchRule({ body: { rule_id: 'rule_1', note: '# some note markdown' } })
+            .expect(200);
+
+          expect(body.rule_source.is_customized).toEqual(true);
+          expect(body.rule_source.type).toEqual('external');
+        });
+
+        it('severity field', async () => {
+          const { body } = await securitySolutionApi
+            .patchRule({ body: { rule_id: 'rule_1', severity: 'medium' } })
+            .expect(200);
+
+          expect(body.rule_source.is_customized).toEqual(true);
+          expect(body.rule_source.type).toEqual('external');
+        });
+
+        it('tags field', async () => {
+          const { body } = await securitySolutionApi
+            .patchRule({ body: { rule_id: 'rule_1', tags: ['red fish', 'blue fish'] } })
+            .expect(200);
+
+          expect(body.rule_source.is_customized).toEqual(true);
+          expect(body.rule_source.type).toEqual('external');
+        });
+
+        it('severity_mapping field', async () => {
+          const { body } = await securitySolutionApi
+            .patchRule({
+              body: {
+                rule_id: 'rule_1',
+                severity_mapping: [
+                  {
+                    field: 'event.severity',
+                    operator: 'equals',
+                    severity: 'low',
+                    value: 'LOW',
+                  },
+                ],
+              },
+            })
+            .expect(200);
+
+          expect(body.rule_source.is_customized).toEqual(true);
+          expect(body.rule_source.type).toEqual('external');
+        });
+
+        it('risk_score field', async () => {
+          const { body } = await securitySolutionApi
+            .patchRule({ body: { rule_id: 'rule_1', risk_score: 72 } })
+            .expect(200);
+
+          expect(body.rule_source.is_customized).toEqual(true);
+          expect(body.rule_source.type).toEqual('external');
+        });
+
+        it('risk_score_mapping field', async () => {
+          const { body } = await securitySolutionApi
+            .patchRule({
+              body: {
+                rule_id: 'rule_1',
+                risk_score_mapping: [{ field: 'event.risk_score', operator: 'equals', value: '' }],
+              },
+            })
+            .expect(200);
+
+          expect(body.rule_source.is_customized).toEqual(true);
+          expect(body.rule_source.type).toEqual('external');
+        });
+
+        it('references field', async () => {
+          const { body } = await securitySolutionApi
+            .patchRule({ body: { rule_id: 'rule_1', references: ['http://test.test'] } })
+            .expect(200);
+
+          expect(body.rule_source.is_customized).toEqual(true);
+          expect(body.rule_source.type).toEqual('external');
+        });
+
+        it('false_positives field', async () => {
+          const { body } = await securitySolutionApi
+            .patchRule({ body: { rule_id: 'rule_1', false_positives: ['false positive example'] } })
+            .expect(200);
+
+          expect(body.rule_source.is_customized).toEqual(true);
+          expect(body.rule_source.type).toEqual('external');
+        });
+
+        it('threat field', async () => {
+          const { body } = await securitySolutionApi
+            .patchRule({
+              body: {
+                rule_id: 'rule_1',
+                threat: [
+                  {
+                    framework: 'MITRE ATT&CK',
+                    tactic: {
+                      id: 'TA0000',
+                      name: 'test tactic',
+                      reference: 'https://attack.mitre.org/tactics/TA0000/',
+                    },
+                  },
+                ],
+              },
+            })
+            .expect(200);
+
+          expect(body.rule_source.is_customized).toEqual(true);
+          expect(body.rule_source.type).toEqual('external');
+        });
+
+        it('setup field', async () => {
+          const { body } = await securitySolutionApi
+            .patchRule({ body: { rule_id: 'rule_1', setup: '# some setup markdown' } })
+            .expect(200);
+
+          expect(body.rule_source.is_customized).toEqual(true);
+          expect(body.rule_source.type).toEqual('external');
+        });
+
+        it('related_integrations field', async () => {
+          const { body } = await securitySolutionApi
+            .patchRule({
+              body: {
+                rule_id: 'rule_1',
+                related_integrations: [{ package: 'package-a', version: '^1.2.3' }],
+              },
+            })
+            .expect(200);
+
+          expect(body.rule_source.is_customized).toEqual(true);
+          expect(body.rule_source.type).toEqual('external');
+        });
+
+        it('required_fields field', async () => {
+          const { body } = await securitySolutionApi
+            .patchRule({
+              body: {
+                rule_id: 'rule_1',
+                required_fields: [{ name: '@timestamp', type: 'date' }],
+              },
+            })
+            .expect(200);
+
+          expect(body.rule_source.is_customized).toEqual(true);
+          expect(body.rule_source.type).toEqual('external');
+        });
+
+        it('max_signals field', async () => {
+          const { body } = await securitySolutionApi
+            .patchRule({
+              body: {
+                rule_id: 'rule_1',
+                max_signals: 42,
+              },
+            })
+            .expect(200);
+
+          expect(body.rule_source.is_customized).toEqual(true);
+          expect(body.rule_source.type).toEqual('external');
+        });
+
+        it('investigation_fields field', async () => {
+          const { body } = await securitySolutionApi
+            .patchRule({
+              body: { rule_id: 'rule_1', investigation_fields: { field_names: ['blob', 'boop'] } },
+            })
+            .expect(200);
+
+          expect(body.rule_source.is_customized).toEqual(true);
+          expect(body.rule_source.type).toEqual('external');
+        });
+
+        it('rule_name_override field', async () => {
+          const { body } = await securitySolutionApi
+            .patchRule({
+              body: { rule_id: 'rule_1', rule_name_override: 'override string' },
+            })
+            .expect(200);
+
+          expect(body.rule_source.is_customized).toEqual(true);
+          expect(body.rule_source.type).toEqual('external');
+        });
+
+        it('timestamp_override field', async () => {
+          const { body } = await securitySolutionApi
+            .patchRule({
+              body: { rule_id: 'rule_1', timestamp_override: 'event.ingested' },
+            })
+            .expect(200);
+
+          expect(body.rule_source.is_customized).toEqual(true);
+          expect(body.rule_source.type).toEqual('external');
+        });
+
+        it('timeline_template fields', async () => {
+          const { body } = await securitySolutionApi
+            .patchRule({
+              body: { rule_id: 'rule_1', timeline_id: '123', timeline_title: 'timeline title' },
+            })
+            .expect(200);
+
+          expect(body.rule_source.is_customized).toEqual(true);
+          expect(body.rule_source.type).toEqual('external');
+        });
+
+        it('building_block_type field', async () => {
+          const { body } = await securitySolutionApi
+            .patchRule({
+              body: { rule_id: 'rule_1', building_block_type: 'building block string' },
+            })
+            .expect(200);
+
+          expect(body.rule_source.is_customized).toEqual(true);
+          expect(body.rule_source.type).toEqual('external');
+        });
+      });
+
+      describe('query rule fields', () => {
+        beforeEach(async () => {
+          await createPrebuiltRuleAssetSavedObjects(es, [ruleAsset]);
+          await installPrebuiltRules(es, supertest);
+        });
+
+        afterEach(async () => {
+          await deleteAllRules(supertest, log);
+          await deleteAllPrebuiltRuleAssets(es, log);
+        });
+
+        it('query field', async () => {
+          const { body } = await securitySolutionApi
+            .patchRule({
+              body: { rule_id: 'rule_1', query: 'event.action: *' },
+            })
+            .expect(200);
+
+          expect(body.rule_source.is_customized).toEqual(true);
+          expect(body.rule_source.type).toEqual('external');
+        });
+
+        it('language field', async () => {
+          const { body } = await securitySolutionApi
+            .patchRule({
+              body: { rule_id: 'rule_1', language: 'lucene' },
+            })
+            .expect(200);
+
+          expect(body.rule_source.is_customized).toEqual(true);
+          expect(body.rule_source.type).toEqual('external');
+        });
+
+        it('filters field', async () => {
+          const { body } = await securitySolutionApi
+            .patchRule({
+              body: {
+                rule_id: 'rule_1',
+                filters: [
+                  {
+                    meta: {
+                      negate: false,
+                      disabled: false,
+                      type: 'phrase',
+                      key: 'test',
+                      params: {
+                        query: 'value',
+                      },
+                    },
+                    query: {
+                      term: {
+                        field: 'value',
+                      },
+                    },
+                  },
+                ],
+              },
+            })
+            .expect(200);
+
+          expect(body.rule_source.is_customized).toEqual(true);
+          expect(body.rule_source.type).toEqual('external');
+        });
+
+        it('index field', async () => {
+          const { body } = await securitySolutionApi
+            .patchRule({
+              body: { rule_id: 'rule_1', index: ['new-index-pattern-*'] },
+            })
+            .expect(200);
+
+          expect(body.rule_source.is_customized).toEqual(true);
+          expect(body.rule_source.type).toEqual('external');
+        });
+
+        it('data_view_id field', async () => {
+          const { body } = await securitySolutionApi
+            .patchRule({
+              body: { rule_id: 'rule_1', data_view_id: 'new-data-view', index: undefined },
+            })
+            .expect(200);
+
+          expect(body.rule_source.is_customized).toEqual(true);
+          expect(body.rule_source.type).toEqual('external');
+        });
+
+        it('alert_suppression field', async () => {
+          const { body } = await securitySolutionApi
+            .patchRule({
+              body: {
+                rule_id: 'rule_1',
+                alert_suppression: {
+                  group_by: ['host.name'],
+                  duration: { value: 5, unit: 'm' },
+                  missing_fields_strategy: 'suppress',
+                },
+              },
+            })
+            .expect(200);
+
+          expect(body.rule_source.is_customized).toEqual(true);
+          expect(body.rule_source.type).toEqual('external');
+        });
+      });
+
+      describe('eql rule type fields', () => {
+        beforeEach(async () => {
+          const eqlRuleAsset = createRuleAssetSavedObject({
+            ...getPrebuiltRuleMockOfType('eql'),
+            rule_id: 'rule_1',
+          });
+
+          await createPrebuiltRuleAssetSavedObjects(es, [eqlRuleAsset]);
+          await installPrebuiltRules(es, supertest);
+        });
+
+        afterEach(async () => {
+          await deleteAllRules(supertest, log);
+          await deleteAllPrebuiltRuleAssets(es, log);
+        });
+
+        it('event_category_override field', async () => {
+          const { body } = await securitySolutionApi
+            .patchRule({
+              body: {
+                rule_id: 'rule_1',
+                event_category_override: 'host.name',
+              },
+            })
+            .expect(200);
+
+          expect(body.rule_source.is_customized).toEqual(true);
+          expect(body.rule_source.type).toEqual('external');
+        });
+
+        it('timestamp_field field', async () => {
+          const { body } = await securitySolutionApi
+            .patchRule({
+              body: {
+                rule_id: 'rule_1',
+                timestamp_field: 'event.ingested',
+              },
+            })
+            .expect(200);
+
+          expect(body.rule_source.is_customized).toEqual(true);
+          expect(body.rule_source.type).toEqual('external');
+        });
+
+        it('tiebreaker_field field', async () => {
+          const { body } = await securitySolutionApi
+            .patchRule({
+              body: {
+                rule_id: 'rule_1',
+                tiebreaker_field: 'event.ingested',
+              },
+            })
+            .expect(200);
+
+          expect(body.rule_source.is_customized).toEqual(true);
+          expect(body.rule_source.type).toEqual('external');
+        });
+      });
+
+      describe('threat match rule type fields', () => {
+        beforeEach(async () => {
+          const threatMatchRuleAsset = createRuleAssetSavedObject({
+            ...getPrebuiltRuleMockOfType('threat_match'),
+            rule_id: 'rule_1',
+          });
+
+          await createPrebuiltRuleAssetSavedObjects(es, [threatMatchRuleAsset]);
+          await installPrebuiltRules(es, supertest);
+        });
+
+        afterEach(async () => {
+          await deleteAllRules(supertest, log);
+          await deleteAllPrebuiltRuleAssets(es, log);
+        });
+
+        it('threat_index field', async () => {
+          const { body } = await securitySolutionApi
+            .patchRule({
+              body: {
+                rule_id: 'rule_1',
+                type: 'threat_match',
+                threat_index: ['blue fish', 'red fish'],
+              },
+            })
+            .expect(200);
+
+          expect(body.rule_source.is_customized).toEqual(true);
+          expect(body.rule_source.type).toEqual('external');
+        });
+
+        it('threat_mapping field', async () => {
+          const { body } = await securitySolutionApi
+            .patchRule({
+              body: {
+                rule_id: 'rule_1',
+                type: 'threat_match',
+                threat_mapping: [
+                  {
+                    entries: [
+                      {
+                        field: 'Endpoint.capabilities',
+                        type: 'mapping',
+                        value: 'Target.dll.pe.description',
+                      },
+                    ],
+                  },
+                ],
+              },
+            })
+            .expect(200);
+
+          expect(body.rule_source.is_customized).toEqual(true);
+          expect(body.rule_source.type).toEqual('external');
+        });
+
+        it('threat_indicator_path field', async () => {
+          const { body } = await securitySolutionApi
+            .patchRule({
+              body: {
+                rule_id: 'rule_1',
+                type: 'threat_match',
+                threat_indicator_path: 'C:over/there.exe',
+              },
+            })
+            .expect(200);
+
+          expect(body.rule_source.is_customized).toEqual(true);
+          expect(body.rule_source.type).toEqual('external');
+        });
+
+        it('threat_query field', async () => {
+          const { body } = await securitySolutionApi
+            .patchRule({
+              body: {
+                rule_id: 'rule_1',
+                type: 'threat_match',
+                threat_query: 'event.action: *',
+              },
+            })
+            .expect(200);
+
+          expect(body.rule_source.is_customized).toEqual(true);
+          expect(body.rule_source.type).toEqual('external');
+        });
+
+        it('threat_language field', async () => {
+          const { body } = await securitySolutionApi
+            .patchRule({
+              body: {
+                rule_id: 'rule_1',
+                type: 'threat_match',
+                threat_language: 'lucene',
+              },
+            })
+            .expect(200);
+
+          expect(body.rule_source.is_customized).toEqual(true);
+          expect(body.rule_source.type).toEqual('external');
+        });
+
+        it('threat_filters field', async () => {
+          const { body } = await securitySolutionApi
+            .patchRule({
+              body: {
+                rule_id: 'rule_1',
+                type: 'threat_match',
+                threat_filters: [
+                  {
+                    meta: {
+                      negate: false,
+                      disabled: false,
+                      type: 'phrase',
+                      key: 'test',
+                      params: {
+                        query: 'value',
+                      },
+                    },
+                    query: {
+                      term: {
+                        field: 'value',
+                      },
+                    },
+                  },
+                ],
+              },
+            })
+            .expect(200);
+
+          expect(body.rule_source.is_customized).toEqual(true);
+          expect(body.rule_source.type).toEqual('external');
+        });
+      });
+
+      describe('threshold rule type fields', () => {
+        beforeEach(async () => {
+          const thresholdRuleAsset = createRuleAssetSavedObject({
+            ...getPrebuiltRuleMockOfType('threshold'),
+            rule_id: 'rule_1',
+          });
+
+          await createPrebuiltRuleAssetSavedObjects(es, [thresholdRuleAsset]);
+          await installPrebuiltRules(es, supertest);
+        });
+
+        afterEach(async () => {
+          await deleteAllRules(supertest, log);
+          await deleteAllPrebuiltRuleAssets(es, log);
+        });
+
+        it('threshold field', async () => {
+          const { body } = await securitySolutionApi
+            .patchRule({
+              body: {
+                rule_id: 'rule_1',
+                type: 'threshold',
+                threshold: {
+                  field: ['Responses.process.pid'],
+                  value: 100,
+                  cardinality: [{ field: 'host.id', value: 2 }],
+                },
+              },
+            })
+            .expect(200);
+
+          expect(body.rule_source.is_customized).toEqual(true);
+          expect(body.rule_source.type).toEqual('external');
+        });
+      });
+
+      describe('machine learning rule type fields', () => {
+        beforeEach(async () => {
+          const machineLearningRuleAsset = createRuleAssetSavedObject({
+            ...getPrebuiltRuleMockOfType('machine_learning'),
+            rule_id: 'rule_1',
+          });
+
+          await createPrebuiltRuleAssetSavedObjects(es, [machineLearningRuleAsset]);
+          await installPrebuiltRules(es, supertest);
+        });
+
+        afterEach(async () => {
+          await deleteAllRules(supertest, log);
+          await deleteAllPrebuiltRuleAssets(es, log);
+        });
+
+        it('machine_learning_job_id field', async () => {
+          const { body } = await securitySolutionApi
+            .patchRule({
+              body: {
+                rule_id: 'rule_1',
+                type: 'machine_learning',
+                machine_learning_job_id: '123',
+              },
+            })
+            .expect(200);
+
+          expect(body.rule_source.is_customized).toEqual(true);
+          expect(body.rule_source.type).toEqual('external');
+        });
+
+        it('anomaly_threshold field', async () => {
+          const { body } = await securitySolutionApi
+            .patchRule({
+              body: {
+                rule_id: 'rule_1',
+                type: 'machine_learning',
+                anomaly_threshold: 20,
+              },
+            })
+            .expect(200);
+
+          expect(body.rule_source.is_customized).toEqual(true);
+          expect(body.rule_source.type).toEqual('external');
+        });
+      });
+
+      describe('new terms rule type fields', () => {
+        beforeEach(async () => {
+          const newTermsRuleAsset = createRuleAssetSavedObject({
+            ...getPrebuiltRuleMockOfType('new_terms'),
+            rule_id: 'rule_1',
+          });
+
+          await createPrebuiltRuleAssetSavedObjects(es, [newTermsRuleAsset]);
+          await installPrebuiltRules(es, supertest);
+        });
+
+        afterEach(async () => {
+          await deleteAllRules(supertest, log);
+          await deleteAllPrebuiltRuleAssets(es, log);
+        });
+
+        it('new_terms_fields field', async () => {
+          const { body } = await securitySolutionApi
+            .patchRule({
+              body: {
+                rule_id: 'rule_1',
+                type: 'new_terms',
+                new_terms_fields: ['event.action'],
+              },
+            })
+            .expect(200);
+
+          expect(body.rule_source.is_customized).toEqual(true);
+          expect(body.rule_source.type).toEqual('external');
+        });
+
+        it('history_window_start field', async () => {
+          const { body } = await securitySolutionApi
+            .patchRule({
+              body: {
+                rule_id: 'rule_1',
+                type: 'new_terms',
+                history_window_start: 'now-7d',
+              },
+            })
+            .expect(200);
+
+          expect(body.rule_source.is_customized).toEqual(true);
+          expect(body.rule_source.type).toEqual('external');
+        });
+      });
+    });
+
+    describe('is_customized calculation is not affected by', () => {
+      beforeEach(async () => {
+        await createPrebuiltRuleAssetSavedObjects(es, [ruleAsset]);
+        await installPrebuiltRules(es, supertest);
+      });
+
+      afterEach(async () => {
+        await deleteAllRules(supertest, log);
+        await deleteAllPrebuiltRuleAssets(es, log);
+      });
+
+      it('actions field', async () => {
+        // create connector/action
+        const createConnector = async (payload: Record<string, unknown>) =>
+          (
+            await supertest
+              .post('/api/actions/action')
+              .set('kbn-xsrf', 'true')
+              .send(payload)
+              .expect(200)
+          ).body;
+
+        const createWebHookConnector = () => createConnector(getWebHookAction());
+
+        const webHookAction = await createWebHookConnector();
+
+        const defaultRuleAction = {
+          id: webHookAction.id,
+          action_type_id: '.webhook' as const,
+          group: 'default' as const,
+          params: {
+            body: '{"test":"a default action"}',
+          },
+          frequency: {
+            notifyWhen: 'onThrottleInterval' as const,
+            summary: true,
+            throttle: '1h' as const,
+          },
+          uuid: 'd487ec3d-05f2-44ad-8a68-11c97dc92202',
+        };
+
+        const { body } = await securitySolutionApi
+          .patchRule({
+            body: {
+              rule_id: 'rule_1',
+              actions: [defaultRuleAction],
+            },
+          })
+          .expect(200);
+
+        expect(body.rule_source.is_customized).toEqual(false);
+        expect(body.rule_source.type).toEqual('external');
+      });
+
+      it('exceptions_list field', async () => {
+        const { body } = await securitySolutionApi
+          .patchRule({
+            body: {
+              rule_id: 'rule_1',
+              exceptions_list: [
+                {
+                  id: 'some_uuid',
+                  list_id: 'list_id_single',
+                  namespace_type: 'single',
+                  type: 'detection',
+                },
+              ],
+            },
+          })
+          .expect(200);
+
+        expect(body.rule_source.is_customized).toEqual(false);
+        expect(body.rule_source.type).toEqual('external');
+      });
+
+      it('enabled field', async () => {
+        const { body } = await securitySolutionApi
+          .patchRule({
+            body: {
+              rule_id: 'rule_1',
+              enabled: true,
+            },
+          })
+          .expect(200);
+
+        expect(body.rule_source.is_customized).toEqual(false);
+        expect(body.rule_source.type).toEqual('external');
+      });
+
+      it('meta field', async () => {
+        const { body } = await securitySolutionApi
+          .patchRule({
+            body: {
+              rule_id: 'rule_1',
+              meta: {
+                severity_override_field: 'field',
+              },
+            },
+          })
+          .expect(200);
+
+        expect(body.rule_source.is_customized).toEqual(false);
+        expect(body.rule_source.type).toEqual('external');
+      });
+    });
+
+    describe('cannot change non-customizable rule fields', () => {
+      beforeEach(async () => {
+        await createPrebuiltRuleAssetSavedObjects(es, [ruleAsset]);
+        await installPrebuiltRules(es, supertest);
+      });
+
+      afterEach(async () => {
+        await deleteAllRules(supertest, log);
+        await deleteAllPrebuiltRuleAssets(es, log);
+      });
+
+      it('id field', async () => {
+        await securitySolutionApi
+          .patchRule({
+            body: {
+              rule_id: 'rule_1',
+              id: 'new-id',
+            },
+          })
+          .expect(400);
+      });
+
+      it('author field', async () => {
+        await securitySolutionApi
+          .patchRule({
+            body: {
+              rule_id: 'rule_1',
+              author: ['new author'],
+            },
+          })
+          .expect(400);
+      });
+
+      it('license field', async () => {
+        await securitySolutionApi
+          .patchRule({
+            body: {
+              rule_id: 'rule_1',
+              license: 'custom-license',
+            },
+          })
+          .expect(400);
+      });
+    });
+
+    describe('user can revert a customized prebuilt rule to its non-customized state', () => {
+      beforeEach(async () => {
+        await createPrebuiltRuleAssetSavedObjects(es, [ruleAsset]);
+        await installPrebuiltRules(es, supertest);
+      });
+
+      afterEach(async () => {
+        await deleteAllRules(supertest, log);
+        await deleteAllPrebuiltRuleAssets(es, log);
+      });
+
+      it('using name field', async () => {
+        // Modify the prebuilt rule
+        const { body: customizedRuleBody } = await securitySolutionApi
+          .patchRule({ body: { rule_id: 'rule_1', name: 'new name' } })
+          .expect(200);
+
+        expect(customizedRuleBody.rule_source.is_customized).toEqual(true);
+        expect(customizedRuleBody.rule_source.type).toEqual('external');
+
+        // Change the name field back to the original value
+        const { body: nonCustomizedRuleBody } = await securitySolutionApi
+          .patchRule({ body: { rule_id: 'rule_1', name: getPrebuiltRuleMock().name } })
+          .expect(200);
+
+        expect(nonCustomizedRuleBody.rule_source.is_customized).toEqual(false);
+        expect(nonCustomizedRuleBody.rule_source.type).toEqual('external');
+      });
+    });
+  });
+};