diff --git a/src/main/java/li/cil/oc/api/event/NetworkActivityEvent.java b/src/main/java/li/cil/oc/api/event/NetworkActivityEvent.java
new file mode 100644
index 000000000..e6ce5cfe9
--- /dev/null
+++ b/src/main/java/li/cil/oc/api/event/NetworkActivityEvent.java
@@ -0,0 +1,158 @@
+package li.cil.oc.api.event;
+
+import cpw.mods.fml.common.eventhandler.Event;
+import li.cil.oc.api.network.Node;
+import net.minecraft.nbt.NBTTagCompound;
+import net.minecraft.tileentity.TileEntity;
+import net.minecraft.world.World;
+
+/**
+ * Events for handling network activity and representing it on the client.
+ * <p/>
+ * This is used to render network activity
+ * indicators on some containers (e.g. computer, server).
+ * <p/>
+ * Use this to implement rendering of disk access indicators on you own
+ * containers / computers / drive bays.
+ * <p/>
+ * Canceling this event is provided to allow registering higher priority
+ * event handlers that override default behavior.
+ */
+public class NetworkActivityEvent extends Event {
+    protected World world;
+
+    protected double x;
+
+    protected double y;
+
+    protected double z;
+
+    protected TileEntity tileEntity;
+
+    protected NBTTagCompound data;
+
+    /**
+     * Constructor for tile entity hosted network cards.
+     *
+     * @param tileEntity the tile entity hosting the network card.
+     * @param data       the additional data.
+     */
+    protected NetworkActivityEvent(TileEntity tileEntity, NBTTagCompound data) {
+        this.world = tileEntity.getWorldObj();
+        this.x = tileEntity.xCoord + 0.5;
+        this.y = tileEntity.yCoord + 0.5;
+        this.z = tileEntity.zCoord + 0.5;
+        this.tileEntity = tileEntity;
+        this.data = data;
+    }
+
+    /**
+     * Constructor for arbitrarily hosted network cards.
+     *
+     * @param world the world the network card lives in.
+     * @param x     the x coordinate of the network card's container.
+     * @param y     the y coordinate of the network card's container.
+     * @param z     the z coordinate of the network card's container.
+     * @param data  the additional data.
+     */
+    protected NetworkActivityEvent(World world, double x, double y, double z, NBTTagCompound data) {
+        this.world = world;
+        this.x = x;
+        this.y = y;
+        this.z = z;
+        this.tileEntity = null;
+        this.data = data;
+    }
+
+    /**
+     * The world the network card lives in.
+     */
+    public World getWorld() {
+        return world;
+    }
+
+    /**
+     * The x coordinate of the network card's container.
+     */
+    public double getX() {
+        return x;
+    }
+
+    /**
+     * The y coordinate of the network card's container.
+     */
+    public double getY() {
+        return y;
+    }
+
+    /**
+     * The z coordinate of the network card's container.
+     */
+    public double getZ() {
+        return z;
+    }
+
+    /**
+     * The tile entity hosting the network card.
+     * <p/>
+     * <em>Important</em>: this can be <tt>null</tt>, which is usually the
+     * case when the container is an entity or item.
+     */
+    public TileEntity getTileEntity() {
+        return tileEntity;
+    }
+
+    /**
+     * Addition custom data, this is used to transmit the number of the server
+     * in a server rack the network card lives in, for example.
+     */
+    public NBTTagCompound getData() {
+        return data;
+    }
+
+    public static final class Server extends NetworkActivityEvent {
+        private Node node;
+
+        public Server(TileEntity tileEntity, Node node) {
+            super(tileEntity, new NBTTagCompound());
+            this.node = node;
+        }
+
+        public Server(World world, double x, double y, double z, Node node) {
+            super(world, x, y, z, new NBTTagCompound());
+            this.node = node;
+        }
+
+        /**
+         * The node of the network card that signalled activity.
+         */
+        public Node getNode() {
+            return node;
+        }
+    }
+
+    public static final class Client extends NetworkActivityEvent {
+        /**
+         * Constructor for tile entity hosted network card.
+         *
+         * @param tileEntity the tile entity hosting the network card.
+         * @param data       the additional data.
+         */
+        public Client(TileEntity tileEntity, NBTTagCompound data) {
+            super(tileEntity, data);
+        }
+
+        /**
+         * Constructor for arbitrarily hosted network card.
+         *
+         * @param world the world the file system lives in.
+         * @param x     the x coordinate of the network card's container.
+         * @param y     the y coordinate of the network card's container.
+         * @param z     the z coordinate of the network card's container.
+         * @param data  the additional data.
+         */
+        public Client(World world, double x, double y, double z, NBTTagCompound data) {
+            super(world, x, y, z, data);
+        }
+    }
+}
diff --git a/src/main/resources/assets/opencomputers/textures/blocks/ServerFrontNetworkActivity.png b/src/main/resources/assets/opencomputers/textures/blocks/ServerFrontNetworkActivity.png
new file mode 100644
index 000000000..10351f509
Binary files /dev/null and b/src/main/resources/assets/opencomputers/textures/blocks/ServerFrontNetworkActivity.png differ
diff --git a/src/main/scala/li/cil/oc/client/PacketHandler.scala b/src/main/scala/li/cil/oc/client/PacketHandler.scala
index acf09a786..95a54c035 100644
--- a/src/main/scala/li/cil/oc/client/PacketHandler.scala
+++ b/src/main/scala/li/cil/oc/client/PacketHandler.scala
@@ -7,7 +7,7 @@ import cpw.mods.fml.common.network.FMLNetworkEvent.ClientCustomPacketEvent
 import li.cil.oc.Localization
 import li.cil.oc.Settings
 import li.cil.oc.api
-import li.cil.oc.api.event.FileSystemAccessEvent
+import li.cil.oc.api.event.{NetworkActivityEvent, FileSystemAccessEvent}
 import li.cil.oc.client.renderer.PetRenderer
 import li.cil.oc.common.Loot
 import li.cil.oc.common.PacketType
@@ -63,6 +63,7 @@ object PacketHandler extends CommonPacketHandler {
       case PacketType.NanomachinesInputs => onNanomachinesInputs(p)
       case PacketType.NanomachinesPower => onNanomachinesPower(p)
       case PacketType.NetSplitterState => onNetSplitterState(p)
+      case PacketType.NetworkActivity => onNetworkActivity(p)
       case PacketType.ParticleEffect => onParticleEffect(p)
       case PacketType.PetVisibility => onPetVisibility(p)
       case PacketType.PowerState => onPowerState(p)
@@ -173,6 +174,23 @@ object PacketHandler extends CommonPacketHandler {
     }
   }
 
+  def onNetworkActivity(p: PacketParser) = {
+    val data = CompressedStreamTools.read(p)
+    if (p.readBoolean()) p.readTileEntity[net.minecraft.tileentity.TileEntity]() match {
+      case Some(t) =>
+        MinecraftForge.EVENT_BUS.post(new NetworkActivityEvent.Client(t, data))
+      case _ => // Invalid packet.
+    }
+    else world(p.player, p.readInt()) match {
+      case Some(world) =>
+        val x = p.readDouble()
+        val y = p.readDouble()
+        val z = p.readDouble()
+        MinecraftForge.EVENT_BUS.post(new NetworkActivityEvent.Client(world, x, y, z, data))
+      case _ => // Invalid packet.
+    }
+  }
+
   def onFloppyChange(p: PacketParser) =
     p.readTileEntity[DiskDrive]() match {
       case Some(t) => t.setInventorySlotContents(0, p.readItemStack())
diff --git a/src/main/scala/li/cil/oc/client/Textures.scala b/src/main/scala/li/cil/oc/client/Textures.scala
index 20f871315..fdfffebb1 100644
--- a/src/main/scala/li/cil/oc/client/Textures.scala
+++ b/src/main/scala/li/cil/oc/client/Textures.scala
@@ -63,6 +63,7 @@ object Textures {
   val blockRackServerOn = new ResourceLocation(Settings.resourceDomain, "textures/blocks/ServerFrontOn.png")
   val blockRackServerError = new ResourceLocation(Settings.resourceDomain, "textures/blocks/ServerFrontError.png")
   val blockRackServerActivity = new ResourceLocation(Settings.resourceDomain, "textures/blocks/ServerFrontActivity.png")
+  val blockRackServerNetworkActivity = new ResourceLocation(Settings.resourceDomain, "textures/blocks/ServerFrontNetworkActivity.png")
   val blockRackTerminalServerOn = new ResourceLocation(Settings.resourceDomain, "textures/blocks/TerminalServerFrontOn.png")
   val blockRackTerminalServerPresence = new ResourceLocation(Settings.resourceDomain, "textures/blocks/TerminalServerFrontPresence.png")
 
diff --git a/src/main/scala/li/cil/oc/client/renderer/tileentity/CaseRenderer.scala b/src/main/scala/li/cil/oc/client/renderer/tileentity/CaseRenderer.scala
index b1fc8ba57..e578b083f 100644
--- a/src/main/scala/li/cil/oc/client/renderer/tileentity/CaseRenderer.scala
+++ b/src/main/scala/li/cil/oc/client/renderer/tileentity/CaseRenderer.scala
@@ -37,7 +37,7 @@ object CaseRenderer extends TileEntitySpecialRenderer {
 
     if (computer.isRunning) {
       renderFrontOverlay(Textures.blockCaseFrontOn)
-      if (System.currentTimeMillis() - computer.lastAccess < 400 && computer.world.rand.nextDouble() > 0.1) {
+      if (System.currentTimeMillis() - computer.lastFileSystemAccess < 400 && computer.world.rand.nextDouble() > 0.1) {
         renderFrontOverlay(Textures.blockCaseFrontActivity)
       }
     }
diff --git a/src/main/scala/li/cil/oc/common/PacketType.scala b/src/main/scala/li/cil/oc/common/PacketType.scala
index dd1f94ab8..3e03c09a6 100644
--- a/src/main/scala/li/cil/oc/common/PacketType.scala
+++ b/src/main/scala/li/cil/oc/common/PacketType.scala
@@ -27,6 +27,7 @@ object PacketType extends Enumeration {
   NanomachinesInputs,
   NanomachinesPower,
   NetSplitterState,
+  NetworkActivity,
   ParticleEffect,
   PetVisibility, // Goes both ways.
   PowerState,
diff --git a/src/main/scala/li/cil/oc/common/event/FileSystemAccessHandler.scala b/src/main/scala/li/cil/oc/common/event/FileSystemAccessHandler.scala
index c065ba41e..626bad367 100644
--- a/src/main/scala/li/cil/oc/common/event/FileSystemAccessHandler.scala
+++ b/src/main/scala/li/cil/oc/common/event/FileSystemAccessHandler.scala
@@ -20,7 +20,7 @@ object FileSystemAccessHandler {
             case server: Server =>
               val containsNode = server.componentSlot(e.getNode.address) >= 0
               if (containsNode) {
-                server.lastAccess = System.currentTimeMillis()
+                server.lastFileSystemAccess = System.currentTimeMillis()
                 t.markChanged(slot)
               }
             case diskDrive: DiskDriveMountable =>
@@ -42,7 +42,7 @@ object FileSystemAccessHandler {
     e.getWorld.playSound(e.getX, e.getY, e.getZ, e.getSound, volume, 1, false)
     e.getTileEntity match {
       case t: DiskDrive => t.lastAccess = System.currentTimeMillis()
-      case t: Case => t.lastAccess = System.currentTimeMillis()
+      case t: Case => t.lastFileSystemAccess = System.currentTimeMillis()
       case t: Raid => t.lastAccess = System.currentTimeMillis()
       case _ =>
     }
diff --git a/src/main/scala/li/cil/oc/common/event/NetworkActivityHandler.scala b/src/main/scala/li/cil/oc/common/event/NetworkActivityHandler.scala
new file mode 100644
index 000000000..c0d76fc60
--- /dev/null
+++ b/src/main/scala/li/cil/oc/common/event/NetworkActivityHandler.scala
@@ -0,0 +1,36 @@
+package li.cil.oc.common.event
+
+import cpw.mods.fml.common.eventhandler.SubscribeEvent
+import li.cil.oc.api.event.NetworkActivityEvent
+import li.cil.oc.api.internal.Rack
+import li.cil.oc.common.tileentity.Case
+import li.cil.oc.server.component.Server
+
+object NetworkActivityHandler {
+  @SubscribeEvent
+  def onNetworkActivity(e: NetworkActivityEvent.Server) {
+    e.getTileEntity match {
+      case t: Rack =>
+        for (slot <- 0 until t.getSizeInventory) {
+          t.getMountable(slot) match {
+            case server: Server =>
+              val containsNode = server.componentSlot(e.getNode.address) >= 0
+              if (containsNode) {
+                server.lastNetworkActivity = System.currentTimeMillis()
+                t.markChanged(slot)
+              }
+            case _ =>
+          }
+        }
+      case _ =>
+    }
+  }
+
+  @SubscribeEvent
+  def onNetworkActivity(e: NetworkActivityEvent.Client) {
+    e.getTileEntity match {
+      case t: Case => t.lastNetworkActivity = System.currentTimeMillis();
+      case _ =>
+    }
+  }
+}
diff --git a/src/main/scala/li/cil/oc/common/event/RackMountableRenderHandler.scala b/src/main/scala/li/cil/oc/common/event/RackMountableRenderHandler.scala
index f525a42fd..8f63d93ba 100644
--- a/src/main/scala/li/cil/oc/common/event/RackMountableRenderHandler.scala
+++ b/src/main/scala/li/cil/oc/common/event/RackMountableRenderHandler.scala
@@ -75,9 +75,12 @@ object RackMountableRenderHandler {
       if (e.data.getBoolean("hasErrored") && RenderUtil.shouldShowErrorLight(e.rack.hashCode * (e.mountable + 1))) {
         e.renderOverlay(Textures.blockRackServerError)
       }
-      if (System.currentTimeMillis() - e.data.getLong("lastAccess") < 400 && e.rack.world.rand.nextDouble() > 0.1) {
+      if (System.currentTimeMillis() - e.data.getLong("lastFileSystemAccess") < 400 && e.rack.world.rand.nextDouble() > 0.1) {
         e.renderOverlay(Textures.blockRackServerActivity)
       }
+      if (!(System.currentTimeMillis() - e.data.getLong("lastNetworkActivity") < 300 && System.currentTimeMillis() % 200 > 100) && e.data.getBoolean("isRunning")) {
+        e.renderOverlay(Textures.blockRackServerNetworkActivity)
+      }
 
       RenderState.enableLighting()
     }
diff --git a/src/main/scala/li/cil/oc/common/tileentity/Case.scala b/src/main/scala/li/cil/oc/common/tileentity/Case.scala
index 2c37414f2..2904bc106 100644
--- a/src/main/scala/li/cil/oc/common/tileentity/Case.scala
+++ b/src/main/scala/li/cil/oc/common/tileentity/Case.scala
@@ -19,8 +19,9 @@ import net.minecraftforge.common.util.ForgeDirection
 class Case(var tier: Int) extends traits.PowerAcceptor with traits.Computer with traits.Colored with internal.Case {
   def this() = this(0)
 
-  // Used on client side to check whether to render disk activity indicators.
-  var lastAccess = 0L
+  // Used on client side to check whether to render disk activity/network indicators.
+  var lastFileSystemAccess = 0L
+  var lastNetworkActivity = 0L
 
   color = Color.byTier(tier)
 
diff --git a/src/main/scala/li/cil/oc/integration/opencomputers/ModOpenComputers.scala b/src/main/scala/li/cil/oc/integration/opencomputers/ModOpenComputers.scala
index 7ce829940..98eae5eec 100644
--- a/src/main/scala/li/cil/oc/integration/opencomputers/ModOpenComputers.scala
+++ b/src/main/scala/li/cil/oc/integration/opencomputers/ModOpenComputers.scala
@@ -86,6 +86,7 @@ object ModOpenComputers extends ModProxy {
     MinecraftForge.EVENT_BUS.register(HoverBootsHandler)
     MinecraftForge.EVENT_BUS.register(Loot)
     MinecraftForge.EVENT_BUS.register(NanomachinesHandler.Common)
+    MinecraftForge.EVENT_BUS.register(NetworkActivityHandler)
     MinecraftForge.EVENT_BUS.register(RobotCommonHandler)
     MinecraftForge.EVENT_BUS.register(SaveHandler)
     MinecraftForge.EVENT_BUS.register(Tablet)
diff --git a/src/main/scala/li/cil/oc/server/PacketSender.scala b/src/main/scala/li/cil/oc/server/PacketSender.scala
index bf9a8e664..07c3a5828 100644
--- a/src/main/scala/li/cil/oc/server/PacketSender.scala
+++ b/src/main/scala/li/cil/oc/server/PacketSender.scala
@@ -1,7 +1,7 @@
 package li.cil.oc.server
 
 import li.cil.oc.api
-import li.cil.oc.api.event.FileSystemAccessEvent
+import li.cil.oc.api.event.{NetworkActivityEvent, FileSystemAccessEvent}
 import li.cil.oc.api.network.EnvironmentHost
 import li.cil.oc.api.network.Node
 import li.cil.oc.common._
@@ -135,6 +135,34 @@ object PacketSender {
     }
   }
 
+  def sendNetworkActivity(node: Node, host: EnvironmentHost) = {
+
+    val event = host match {
+      case t: net.minecraft.tileentity.TileEntity => new NetworkActivityEvent.Server(t, node)
+      case _ => new NetworkActivityEvent.Server(host.world, host.xPosition, host.yPosition, host.zPosition, node)
+    }
+    MinecraftForge.EVENT_BUS.post(event)
+    if (!event.isCanceled) {
+
+      val pb = new SimplePacketBuilder(PacketType.NetworkActivity)
+
+      CompressedStreamTools.write(event.getData, pb)
+      event.getTileEntity match {
+        case t: net.minecraft.tileentity.TileEntity =>
+          pb.writeBoolean(true)
+          pb.writeTileEntity(t)
+        case _ =>
+          pb.writeBoolean(false)
+          pb.writeInt(event.getWorld.provider.dimensionId)
+          pb.writeDouble(event.getX)
+          pb.writeDouble(event.getY)
+          pb.writeDouble(event.getZ)
+      }
+
+      pb.sendToPlayersNearHost(host, Option(64))
+    }
+  }
+
   def sendFloppyChange(t: tileentity.DiskDrive, stack: ItemStack = null) {
     val pb = new SimplePacketBuilder(PacketType.FloppyChange)
 
diff --git a/src/main/scala/li/cil/oc/server/component/NetworkCard.scala b/src/main/scala/li/cil/oc/server/component/NetworkCard.scala
index 9dd697207..591effe42 100644
--- a/src/main/scala/li/cil/oc/server/component/NetworkCard.scala
+++ b/src/main/scala/li/cil/oc/server/component/NetworkCard.scala
@@ -12,6 +12,7 @@ import li.cil.oc.api.machine.Context
 import li.cil.oc.api.network.EnvironmentHost
 import li.cil.oc.api.network._
 import li.cil.oc.api.prefab
+import li.cil.oc.server.{PacketSender => ServerPacketSender}
 import net.minecraft.nbt._
 
 import scala.collection.convert.WrapAsScala._
@@ -73,6 +74,7 @@ class NetworkCard(val host: EnvironmentHost) extends prefab.ManagedEnvironment w
     val port = checkPort(args.checkInteger(1))
     val packet = api.Network.newPacket(node.address, address, port, args.drop(2).toArray)
     doSend(packet)
+    networkActivity()
     result(true)
   }
 
@@ -81,6 +83,7 @@ class NetworkCard(val host: EnvironmentHost) extends prefab.ManagedEnvironment w
     val port = checkPort(args.checkInteger(0))
     val packet = api.Network.newPacket(node.address, null, port, args.drop(1).toArray)
     doBroadcast(packet)
+    networkActivity()
     result(true)
   }
 
@@ -137,6 +140,7 @@ class NetworkCard(val host: EnvironmentHost) extends prefab.ManagedEnvironment w
     if (packet.source != node.address && Option(packet.destination).forall(_ == node.address)) {
       if (openPorts.contains(packet.port)) {
         node.sendToReachable("computer.signal", Seq("modem_message", packet.source, Int.box(packet.port), Double.box(distance)) ++ packet.data: _*)
+        networkActivity()
       }
       // Accept wake-up messages regardless of port because we close all ports
       // when our computer shuts down.
@@ -184,4 +188,11 @@ class NetworkCard(val host: EnvironmentHost) extends prefab.ManagedEnvironment w
   protected def checkPort(port: Int) =
     if (port < 1 || port > 0xFFFF) throw new IllegalArgumentException("invalid port number")
     else port
+
+  private def networkActivity() {
+    host match {
+      case (h) => ServerPacketSender.sendNetworkActivity(node, h)
+      case _ =>
+    }
+  }
 }
diff --git a/src/main/scala/li/cil/oc/server/component/Server.scala b/src/main/scala/li/cil/oc/server/component/Server.scala
index f5cedf57b..339fb3bd6 100644
--- a/src/main/scala/li/cil/oc/server/component/Server.scala
+++ b/src/main/scala/li/cil/oc/server/component/Server.scala
@@ -38,7 +38,8 @@ class Server(val rack: tileentity.Rack, val slot: Int) extends Environment with
 
   var wasRunning = false
   var hadErrored = false
-  var lastAccess = 0L
+  var lastFileSystemAccess = 0L
+  var lastNetworkActivity = 0L
 
   // ----------------------------------------------------------------------- //
   // Environment
@@ -142,7 +143,8 @@ class Server(val rack: tileentity.Rack, val slot: Int) extends Environment with
     val nbt = new NBTTagCompound()
     nbt.setBoolean("isRunning", wasRunning)
     nbt.setBoolean("hasErrored", hadErrored)
-    nbt.setLong("lastAccess", lastAccess)
+    nbt.setLong("lastFileSystemAccess", lastFileSystemAccess)
+    nbt.setLong("lastNetworkActivity", lastNetworkActivity)
     nbt
   }