diff --git a/static/js/modules/interface/main.js b/static/js/modules/interface/main.js
index 352c9e5..6369ae9 100644
--- a/static/js/modules/interface/main.js
+++ b/static/js/modules/interface/main.js
@@ -49,6 +49,14 @@ document.addEventListener("DOMContentLoaded", () => {
                 window.console.error(`Signature invalid! Ignoring packet ${data.id}.`);
                 return;
             }
+
+            // check if the packet is replayed.
+            if (data.timestamp <= sender.lastPacket) {
+                window.console.error(`Replay detected! Ignoring packet ${data.id}.`);
+                return;
+            }
+
+            sender.lastPacket = data.timestamp;
         }
 
         switch (data.type) {
diff --git a/static/js/modules/interface/packet.js b/static/js/modules/interface/packet.js
index 0f355c0..2e37621 100644
--- a/static/js/modules/interface/packet.js
+++ b/static/js/modules/interface/packet.js
@@ -5,6 +5,7 @@ export class Packet {
         return {
             type: name,
             id: window.crypto.randomUUID(),
+            timestamp: Date.now(),
             author: ID,
         };
     }
diff --git a/static/js/modules/interface/player.js b/static/js/modules/interface/player.js
index 988d489..c19c233 100644
--- a/static/js/modules/interface/player.js
+++ b/static/js/modules/interface/player.js
@@ -19,6 +19,7 @@ export class Player {
         this.id = id;
         this.ready = false;
         this.rsaPubKey = RsaPubKey.fromJSON(pubkey);
+        this.lastPacket = 0;
 
         // Data which is reset every turn
         this.isPlaying = false;