diff --git a/entrypoint.example.ts b/entrypoint.example.ts
index d933176..61fe279 100644
--- a/entrypoint.example.ts
+++ b/entrypoint.example.ts
@@ -3,6 +3,7 @@
 import {
   antiDuplicationPolicy,
   hellthreadPolicy,
+  keywordPolicy,
   noopPolicy,
   pipeline,
   pubkeyBanPolicy,
@@ -18,6 +19,7 @@ for await (const msg of readStdin()) {
     [antiDuplicationPolicy, { ttl: 60000, minLength: 50 }],
     [rateLimitPolicy, { whitelist: ['127.0.0.1'] }],
     [pubkeyBanPolicy, ['e810fafa1e89cdf80cced8e013938e87e21b699b24c8570537be92aec4b12c18']],
+    [keywordPolicy, ['https://t.me/']],
   ]);
 
   writeStdout(result);
diff --git a/mod.ts b/mod.ts
index bef8ed9..b5f080f 100644
--- a/mod.ts
+++ b/mod.ts
@@ -1,9 +1,11 @@
 export { default as antiDuplicationPolicy } from './src/policies/anti-duplication-policy.ts';
 export { default as hellthreadPolicy } from './src/policies/hellthread-policy.ts';
+export { default as keywordPolicy } from './src/policies/keyword-policy.ts';
 export { default as noopPolicy } from './src/policies/noop-policy.ts';
 export { default as pubkeyBanPolicy } from './src/policies/pubkey-ban-policy.ts';
 export { default as rateLimitPolicy } from './src/policies/rate-limit-policy.ts';
 export { default as readOnlyPolicy } from './src/policies/read-only-policy.ts';
+export { default as whitelistPolicy } from './src/policies/whitelist-policy.ts';
 
 export { readStdin, writeStdout } from './src/io.ts';
 export { default as pipeline } from './src/pipeline.ts';
diff --git a/src/policies/keyword-policy.test.ts b/src/policies/keyword-policy.test.ts
new file mode 100644
index 0000000..f33f7df
--- /dev/null
+++ b/src/policies/keyword-policy.test.ts
@@ -0,0 +1,15 @@
+import { assert } from '../deps.ts';
+import { buildEvent, buildInputMessage } from '../test.ts';
+
+import keywordPolicy from './keyword-policy.ts';
+
+Deno.test('blocks banned pubkeys', async () => {
+  const words = ['https://t.me/spam'];
+
+  const msg0 = buildInputMessage();
+  const msg1 = buildInputMessage({ event: buildEvent({ content: '🔥🔥🔥 https://t.me/spam 我想死' }) });
+
+  assert((await keywordPolicy(msg0, words)).action === 'accept');
+  assert((await keywordPolicy(msg1, words)).action === 'reject');
+  assert((await keywordPolicy(msg1, [])).action === 'accept');
+});
diff --git a/src/policies/keyword-policy.ts b/src/policies/keyword-policy.ts
new file mode 100644
index 0000000..7487dd3
--- /dev/null
+++ b/src/policies/keyword-policy.ts
@@ -0,0 +1,29 @@
+import { Policy } from '../types.ts';
+
+/** Reject events containing any of the strings in its content. */
+const keywordPolicy: Policy<Iterable<string>> = ({ event: { id, content } }, words = []) => {
+  let isMatch = false;
+
+  for (const word of words) {
+    if (content.toLocaleLowerCase().includes(word.toLowerCase())) {
+      isMatch = true;
+      break;
+    }
+  }
+
+  if (isMatch) {
+    return {
+      id,
+      action: 'reject',
+      msg: 'Event contains a banned word or phrase.',
+    };
+  }
+
+  return {
+    id,
+    action: 'accept',
+    msg: '',
+  };
+};
+
+export default keywordPolicy;