diff --git a/shell/lock/LockSurface.qml b/shell/lock/LockSurface.qml
index 4abebc8..9520fde 100644
--- a/shell/lock/LockSurface.qml
+++ b/shell/lock/LockSurface.qml
@@ -21,8 +21,11 @@ WlSessionLockSurface {
     readonly property real _threat: {
         if (!_threatEnabled || root.auth.failCount <= 0)
             return 0;
-        const t = Math.min(1.0, root.auth.failCount / 5);
-        return t * t * 0.6; // quadratic: 1->0.024, 2->0.096, 3->0.216, 4->0.384, 5->0.6
+        const levels = [0, 0.05, 0.12, 0.3, 0.45, 0.6];
+        const n = root.auth.failCount;
+        if (n <= 5)
+            return levels[n];
+        return Math.min(1.0, 0.6 + (n - 5) * 0.1);
     }
     property real _heartbeat: 0