diff --git a/history.html b/history.html
index c45955f..8d53049 100644
--- a/history.html
+++ b/history.html
@@ -211,6 +211,25 @@
         right: 0.5em;
       }
 
+      .map .node-alert {
+        -webkit-animation: blink 2s linear;
+        -webkit-animation-iteration-count: infinite;
+        animation: blink 2s linear;
+        animation-iteration-count: infinite;
+      }
+
+      @-webkit-keyframes blink {
+        0%   { opacity: 1.0; }
+        80%  { opacity: 1.0; }
+        90%  { opacity: 0.0; }
+      }
+
+      @keyframes blink {
+        0%   { opacity: 1.0; }
+        80%  { opacity: 1.0; }
+        90%  { opacity: 0.0; }
+      }
+
       @media screen and (max-width: 80em) {
         .sidebar {
           font-size: 0.8em;
diff --git a/lib/map.js b/lib/map.js
index d44a639..35bf2ed 100644
--- a/lib/map.js
+++ b/lib/map.js
@@ -50,6 +50,7 @@ define(function () {
 
    var iconOnline  = { color: "#1566A9", radius: 6, fillOpacity: 0.5, weight: 2, className: "stroke-first" }
    var iconOffline = { color: "#D43E2A", radius: 6, fillOpacity: 0.5, weight: 2, className: "stroke-first" }
+   var iconAlert   = { color: "#D43E2A", radius: 6, fillOpacity: 0.5, weight: 2, className: "stroke-first node-alert" }
    var iconNew     = { color: "#558020", radius: 6, fillOpacity: 0.5, weight: 2, className: "stroke-first" }
 
    var groupOnline, group
@@ -87,6 +88,9 @@ define(function () {
         if (d.flags.online)
           return iconNew
 
+        if (d.lastseen.isAfter(moment(now).subtract(1, 'days')))
+          return iconAlert
+
         return iconOffline
       }, gotoAnything))