diff --git a/LaunchServer/source/LaunchServer.java b/LaunchServer/source/LaunchServer.java
index 53ed341..b1f718e 100644
--- a/LaunchServer/source/LaunchServer.java
+++ b/LaunchServer/source/LaunchServer.java
@@ -281,7 +281,7 @@
 
 				// Sync and sign update dir
 				LogHelper.subInfo("Syncing '%s' update dir", name);
-				HashedDir updateHDir = new HashedDir(updateDir, null);
+				HashedDir updateHDir = new HashedDir(updateDir, null, true);
 				newUpdatesDirMap.put(name, new SignedObjectHolder<>(updateHDir, privateKey));
 			}
 		}
diff --git a/Launcher/source/client/ClientLauncher.java b/Launcher/source/client/ClientLauncher.java
index fa68912..42b01fe 100644
--- a/Launcher/source/client/ClientLauncher.java
+++ b/Launcher/source/client/ClientLauncher.java
@@ -199,7 +199,7 @@
 		}
 
 		// Hash directory and compare (ignore update-only matcher entries, it will break offline-mode)
-		HashedDir currentHDir = new HashedDir(dir, matcher);
+		HashedDir currentHDir = new HashedDir(dir, matcher, false);
 		if (!hdir.diff(currentHDir, matcher).isSame()) {
 			throw new SecurityException(String.format("Forbidden modification: '%s'", IOHelper.getFileName(dir)));
 		}
diff --git a/Launcher/source/hasher/DirWatcher.java b/Launcher/source/hasher/DirWatcher.java
index 69ae552..d165135 100644
--- a/Launcher/source/hasher/DirWatcher.java
+++ b/Launcher/source/hasher/DirWatcher.java
@@ -15,6 +15,7 @@
 import java.util.LinkedList;
 import java.util.Objects;
 
+import com.sun.nio.file.ExtendedWatchEventModifier;
 import com.sun.nio.file.SensitivityWatchEventModifier;
 import launcher.LauncherAPI;
 import launcher.helper.IOHelper;
@@ -22,7 +23,13 @@
 import launcher.helper.LogHelper;
 
 public final class DirWatcher implements Runnable, AutoCloseable {
+	private static final boolean FILE_TREE_SUPPORTED = JVMHelper.OS_TYPE == JVMHelper.OS.MUSTDIE;
+
+	// Constants
 	private static final WatchEvent.Modifier[] MODIFIERS = { SensitivityWatchEventModifier.HIGH };
+	private static final WatchEvent.Modifier[] FILE_TREE_MODIFIERS = {
+		ExtendedWatchEventModifier.FILE_TREE, SensitivityWatchEventModifier.HIGH
+	};
 	private static final WatchEvent.Kind<?>[] KINDS = {
 		StandardWatchEventKinds.ENTRY_CREATE, StandardWatchEventKinds.ENTRY_MODIFY, StandardWatchEventKinds.ENTRY_DELETE
 	};
@@ -38,9 +45,15 @@
 		this.dir = Objects.requireNonNull(dir, "dir");
 		this.hdir = Objects.requireNonNull(hdir, "hdir");
 		this.matcher = matcher;
+		service = dir.getFileSystem().newWatchService();
+
+		// Use FILE_TREE if supported
+		if (FILE_TREE_SUPPORTED) {
+			dir.register(service, KINDS, FILE_TREE_MODIFIERS);
+			return;
+		}
 
 		// Register dirs recursively
-		service = dir.getFileSystem().newWatchService();
 		IOHelper.walk(dir, new RegisterFileVisitor(), true);
 	}
 
diff --git a/Launcher/source/hasher/HashedDir.java b/Launcher/source/hasher/HashedDir.java
index f54bdb4..ec6c3d9 100644
--- a/Launcher/source/hasher/HashedDir.java
+++ b/Launcher/source/hasher/HashedDir.java
@@ -27,8 +27,8 @@
 	}
 
 	@LauncherAPI
-	public HashedDir(Path dir, FileNameMatcher matcher) throws IOException {
-		IOHelper.walk(dir, new HashFileVisitor(dir, matcher), true);
+	public HashedDir(Path dir, FileNameMatcher matcher, boolean allowSymlinks) throws IOException {
+		IOHelper.walk(dir, new HashFileVisitor(dir, matcher, allowSymlinks), true);
 	}
 
 	@LauncherAPI
@@ -173,15 +173,17 @@
 	private final class HashFileVisitor extends SimpleFileVisitor<Path> {
 		private final Path dir;
 		private final FileNameMatcher matcher;
-		private final Deque<String> path = new LinkedList<>();
-		private final Deque<HashedDir> stack = new LinkedList<>();
+		private final boolean allowSymlinks;
 
 		// State
 		private HashedDir current = HashedDir.this;
+		private final Deque<String> path = new LinkedList<>();
+		private final Deque<HashedDir> stack = new LinkedList<>();
 
-		private HashFileVisitor(Path dir, FileNameMatcher matcher) {
+		private HashFileVisitor(Path dir, FileNameMatcher matcher, boolean allowSymlinks) {
 			this.dir = dir;
 			this.matcher = matcher;
+			this.allowSymlinks = allowSymlinks;
 		}
 
 		@Override
@@ -207,6 +209,12 @@
 				return result;
 			}
 
+			// Verify is not symlink
+			// Symlinks was disallowed because modification of it's destination are ignored by DirWatcher
+			if (!allowSymlinks && attrs.isSymbolicLink()) {
+				throw new SecurityException("Symlinks are not allowed");
+			}
+
 			// Add child
 			stack.add(current);
 			current = new HashedDir();
@@ -218,9 +226,13 @@
 
 		@Override
 		public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) throws IOException {
-			path.add(IOHelper.getFileName(file));
+			// Verify is not symlink
+			if (!allowSymlinks && attrs.isSymbolicLink()) {
+				throw new SecurityException("Symlinks are not allowed");
+			}
 
 			// Add file (may be unhashed, if exclusion)
+			path.add(IOHelper.getFileName(file));
 			boolean hash = matcher == null || matcher.shouldUpdate(path);
 			current.map.put(path.removeLast(), new HashedFile(file, attrs.size(), hash));
 			return super.visitFile(file, attrs);
diff --git a/Launcher/source/request/update/UpdateRequest.java b/Launcher/source/request/update/UpdateRequest.java
index 89672c8..d99335b 100644
--- a/Launcher/source/request/update/UpdateRequest.java
+++ b/Launcher/source/request/update/UpdateRequest.java
@@ -65,7 +65,7 @@
 	@Override
 	public SignedObjectHolder<HashedDir> request() throws Exception {
 		Files.createDirectories(dir);
-		localDir = new HashedDir(dir, matcher);
+		localDir = new HashedDir(dir, matcher, false);
 
 		// Start request
 		return super.request();