diff --git a/x-pack/plugins/endpoint/common/alert_constants.ts b/x-pack/plugins/endpoint/common/alert_constants.ts
index 85e1643d684f2..66de2b85ef3a7 100644
--- a/x-pack/plugins/endpoint/common/alert_constants.ts
+++ b/x-pack/plugins/endpoint/common/alert_constants.ts
@@ -13,10 +13,6 @@ export class AlertConstants {
    * The path for the Alert's Index Pattern API.
    */
   static INDEX_PATTERN_ROUTE = `${AlertConstants.BASE_API_URL}/index_pattern`;
-  /**
-   * Alert's Index pattern
-   */
-  static ALERT_INDEX_NAME = 'events-endpoint-1';
   /**
    * A paramter passed to Alert's Index Pattern.
    */
diff --git a/x-pack/plugins/endpoint/server/routes/alerts/details/handlers.ts b/x-pack/plugins/endpoint/server/routes/alerts/details/handlers.ts
index 92f8aacbf26a2..ab6d1850e425d 100644
--- a/x-pack/plugins/endpoint/server/routes/alerts/details/handlers.ts
+++ b/x-pack/plugins/endpoint/server/routes/alerts/details/handlers.ts
@@ -6,11 +6,11 @@
 import { GetResponse } from 'elasticsearch';
 import { KibanaRequest, RequestHandler } from 'kibana/server';
 import { AlertEvent } from '../../../../common/types';
-import { AlertConstants } from '../../../../common/alert_constants';
 import { EndpointAppContext } from '../../../types';
 import { AlertDetailsRequestParams } from '../types';
 import { AlertDetailsPagination } from './lib';
 import { getHostData } from '../../metadata';
+import { AlertId, AlertIdError } from '../lib';
 
 export const alertDetailsHandlerWrapper = function(
   endpointAppContext: EndpointAppContext
@@ -21,10 +21,10 @@ export const alertDetailsHandlerWrapper = function(
     res
   ) => {
     try {
-      const alertId = req.params.id;
+      const alertId = AlertId.fromEncoded(req.params.id);
       const response = (await ctx.core.elasticsearch.dataClient.callAsCurrentUser('get', {
-        index: AlertConstants.ALERT_INDEX_NAME,
-        id: alertId,
+        index: alertId.index,
+        id: alertId.id,
       })) as GetResponse<AlertEvent>;
 
       const indexPattern = await endpointAppContext.service
@@ -50,7 +50,7 @@ export const alertDetailsHandlerWrapper = function(
 
       return res.ok({
         body: {
-          id: response._id,
+          id: alertId.toString(),
           ...response._source,
           state: {
             host_metadata: currentHostInfo?.metadata,
@@ -60,7 +60,13 @@ export const alertDetailsHandlerWrapper = function(
         },
       });
     } catch (err) {
-      if (err.status === 404) {
+      const logger = endpointAppContext.logFactory.get('alerts');
+      logger.warn(err);
+
+      // err will be an AlertIdError if the passed in alert id is not valid
+      if (err instanceof AlertIdError) {
+        return res.badRequest({ body: err });
+      } else if (err.status === 404) {
         return res.notFound({ body: err });
       }
       return res.internalError({ body: err });
diff --git a/x-pack/plugins/endpoint/server/routes/alerts/details/lib/pagination.ts b/x-pack/plugins/endpoint/server/routes/alerts/details/lib/pagination.ts
index 0f69e1bb60c44..5c95b1217d829 100644
--- a/x-pack/plugins/endpoint/server/routes/alerts/details/lib/pagination.ts
+++ b/x-pack/plugins/endpoint/server/routes/alerts/details/lib/pagination.ts
@@ -8,7 +8,7 @@ import { GetResponse, SearchResponse } from 'elasticsearch';
 import { AlertEvent, AlertHits, AlertAPIOrdering } from '../../../../../common/types';
 import { AlertConstants } from '../../../../../common/alert_constants';
 import { EndpointConfigType } from '../../../../config';
-import { searchESForAlerts, Pagination } from '../../lib';
+import { searchESForAlerts, Pagination, AlertId } from '../../lib';
 import { AlertSearchQuery, SearchCursor, AlertDetailsRequestParams } from '../../types';
 import { BASE_ALERTS_ROUTE } from '../..';
 import { RequestHandlerContext } from '../../../../../../../../src/core/server';
@@ -59,7 +59,8 @@ export class AlertDetailsPagination extends Pagination<
 
   protected getUrlFromHits(hits: AlertHits): string | null {
     if (hits.length > 0) {
-      return `${BASE_ALERTS_ROUTE}/${hits[0]._id}`;
+      const id = new AlertId(hits[0]._index, hits[0]._id);
+      return `${BASE_ALERTS_ROUTE}/${id.toString()}`;
     }
     return null;
   }
diff --git a/x-pack/plugins/endpoint/server/routes/alerts/lib/alert_id.ts b/x-pack/plugins/endpoint/server/routes/alerts/lib/alert_id.ts
new file mode 100644
index 0000000000000..797bf69f5991a
--- /dev/null
+++ b/x-pack/plugins/endpoint/server/routes/alerts/lib/alert_id.ts
@@ -0,0 +1,48 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License;
+ * you may not use this file except in compliance with the Elastic License.
+ */
+import { AlertIdError } from './error';
+
+/**
+ * Abstraction over alert IDs.
+ */
+export class AlertId {
+  protected readonly _index: string;
+  protected readonly _id: string;
+
+  constructor(index: string, id: string) {
+    this._index = index;
+    this._id = id;
+  }
+
+  public get index() {
+    return this._index;
+  }
+
+  public get id() {
+    return this._id;
+  }
+
+  static fromEncoded(encoded: string): AlertId {
+    try {
+      const value = encoded.replace(/\-/g, '+').replace(/_/g, '/');
+      const data = Buffer.from(value, 'base64').toString('utf8');
+      const { index, id } = JSON.parse(data);
+      return new AlertId(index, id);
+    } catch (error) {
+      throw new AlertIdError(`Unable to decode alert id: ${encoded}`);
+    }
+  }
+
+  toString(): string {
+    const value = JSON.stringify({ index: this.index, id: this.id });
+    // replace invalid URL characters with valid ones
+    return Buffer.from(value, 'utf8')
+      .toString('base64')
+      .replace(/\+/g, '-')
+      .replace(/\//g, '_')
+      .replace(/=+$/g, '');
+  }
+}
diff --git a/x-pack/plugins/endpoint/server/routes/alerts/lib/error.ts b/x-pack/plugins/endpoint/server/routes/alerts/lib/error.ts
new file mode 100644
index 0000000000000..7b00634b25c9c
--- /dev/null
+++ b/x-pack/plugins/endpoint/server/routes/alerts/lib/error.ts
@@ -0,0 +1,11 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License;
+ * you may not use this file except in compliance with the Elastic License.
+ */
+
+export class AlertIdError extends Error {
+  constructor(message: string) {
+    super(message);
+  }
+}
diff --git a/x-pack/plugins/endpoint/server/routes/alerts/lib/index.ts b/x-pack/plugins/endpoint/server/routes/alerts/lib/index.ts
index 7bc1c0c306ae2..1c98e3c615669 100644
--- a/x-pack/plugins/endpoint/server/routes/alerts/lib/index.ts
+++ b/x-pack/plugins/endpoint/server/routes/alerts/lib/index.ts
@@ -17,7 +17,9 @@ import {
   UndefinedResultPosition,
 } from '../types';
 
+export { AlertIdError } from './error';
 export { Pagination } from './pagination';
+export { AlertId } from './alert_id';
 
 function reverseSortDirection(order: AlertAPIOrdering): AlertAPIOrdering {
   if (order === 'asc') {
diff --git a/x-pack/plugins/endpoint/server/routes/alerts/list/lib/index.ts b/x-pack/plugins/endpoint/server/routes/alerts/list/lib/index.ts
index 114251820ce4b..0af8f6cf792dd 100644
--- a/x-pack/plugins/endpoint/server/routes/alerts/list/lib/index.ts
+++ b/x-pack/plugins/endpoint/server/routes/alerts/list/lib/index.ts
@@ -20,6 +20,7 @@ import { AlertConstants } from '../../../../../common/alert_constants';
 import { EndpointAppContext } from '../../../../types';
 import { AlertSearchQuery } from '../../types';
 import { AlertListPagination } from './pagination';
+import { AlertId } from '../../lib';
 
 export const getRequestData = async (
   request: KibanaRequest<unknown, AlertingIndexGetQueryResult, unknown>,
@@ -105,8 +106,9 @@ export async function mapToAlertResultList(
   const pagination: AlertListPagination = new AlertListPagination(config, reqCtx, reqData, hits);
 
   function mapHit(entry: AlertHits[0]): AlertData {
+    const alertId = new AlertId(entry._index, entry._id);
     return {
-      id: entry._id,
+      id: alertId.toString(),
       ...entry._source,
       prev: null,
       next: null,
diff --git a/x-pack/test/api_integration/apis/endpoint/alerts.ts b/x-pack/test/api_integration/apis/endpoint/alerts.ts
index 7e72a2f9072f3..94aaab2530247 100644
--- a/x-pack/test/api_integration/apis/endpoint/alerts.ts
+++ b/x-pack/test/api_integration/apis/endpoint/alerts.ts
@@ -6,6 +6,7 @@
 import expect from '@kbn/expect/expect.js';
 import { FtrProviderContext } from '../../ftr_provider_context';
 import { AlertData } from '../../../../plugins/endpoint/common/types';
+import { AlertId } from '../../../../plugins/endpoint/server/routes/alerts/lib/index';
 
 /**
  * The number of alert documents in the es archive.
@@ -65,6 +66,7 @@ export default function({ getService }: FtrProviderContext) {
   const nextPrevPrefixOrder = 'order=desc';
   const nextPrevPrefixPageSize = 'page_size=10';
   const nextPrevPrefix = `${nextPrevPrefixQuery}&${nextPrevPrefixDateRange}&${nextPrevPrefixSort}&${nextPrevPrefixOrder}&${nextPrevPrefixPageSize}`;
+  const alertIndex = 'events-endpoint-1';
 
   let nullableEventId = '';
 
@@ -74,7 +76,7 @@ export default function({ getService }: FtrProviderContext) {
         await esArchiver.load('endpoint/alerts/api_feature');
         await esArchiver.load('endpoint/alerts/host_api_feature');
         const res = await es.search({
-          index: 'events-endpoint-1',
+          index: alertIndex,
           body: ES_QUERY_MISSING,
         });
         nullableEventId = res.hits.hits[0]._source.event.id;
@@ -377,36 +379,45 @@ export default function({ getService }: FtrProviderContext) {
       });
 
       it('should return alert details by id, getting last alert', async () => {
-        const documentID = 'zbNm0HABdD75WLjLYgcB';
-        const prevDocumentID = '2rNm0HABdD75WLjLYgcU';
+        const documentID = new AlertId(alertIndex, 'zbNm0HABdD75WLjLYgcB');
+        const prevDocumentID = new AlertId(alertIndex, '2rNm0HABdD75WLjLYgcU');
         const { body } = await supertest
-          .get(`/api/endpoint/alerts/${documentID}`)
+          .get(`/api/endpoint/alerts/${documentID.toString()}`)
           .set('kbn-xsrf', 'xxx')
           .expect(200);
-        expect(body.id).to.eql(documentID);
-        expect(body.prev).to.eql(`/api/endpoint/alerts/${prevDocumentID}`);
+        expect(body.id).to.eql(documentID.toString());
+        expect(body.prev).to.eql(`/api/endpoint/alerts/${prevDocumentID.toString()}`);
         expect(body.next).to.eql(null); // last alert, no more beyond this
         expect(body.state.host_metadata.host.id).to.eql(body.host.id);
       });
 
       it('should return alert details by id, getting first alert', async () => {
-        const documentID = 'p7Nm0HABdD75WLjLYghv';
-        const nextDocumentID = 'mbNm0HABdD75WLjLYgho';
+        const documentID = new AlertId(alertIndex, 'p7Nm0HABdD75WLjLYghv');
+        const nextDocumentID = new AlertId(alertIndex, 'mbNm0HABdD75WLjLYgho');
         const { body } = await supertest
-          .get(`/api/endpoint/alerts/${documentID}`)
+          .get(`/api/endpoint/alerts/${documentID.toString()}`)
           .set('kbn-xsrf', 'xxx')
           .expect(200);
-        expect(body.id).to.eql(documentID);
-        expect(body.next).to.eql(`/api/endpoint/alerts/${nextDocumentID}`);
+        expect(body.id).to.eql(documentID.toString());
+        expect(body.next).to.eql(`/api/endpoint/alerts/${nextDocumentID.toString()}`);
         expect(body.prev).to.eql(null); // first alert, no more before this
       });
 
       it('should return 404 when alert is not found', async () => {
+        const documentID = new AlertId(alertIndex, 'does-not-exit');
+
         await supertest
-          .get('/api/endpoint/alerts/does-not-exist')
+          .get(`/api/endpoint/alerts/${documentID.toString()}`)
           .set('kbn-xsrf', 'xxx')
           .expect(404);
       });
+
+      it('should return 400 when alert id is not valid', async () => {
+        await supertest
+          .get('/api/endpoint/alerts/does-not-exist')
+          .set('kbn-xsrf', 'xxx')
+          .expect(400);
+      });
     });
   });
 }