[SSHD-646] ThreadGroup created in ThreadUtils is not destroyed and causes memory leak
diff --git a/sshd-core/src/main/java/org/apache/sshd/common/util/threads/ThreadUtils.java b/sshd-core/src/main/java/org/apache/sshd/common/util/threads/ThreadUtils.java
index d0a25ed..9008635 100644
--- a/sshd-core/src/main/java/org/apache/sshd/common/util/threads/ThreadUtils.java
+++ b/sshd-core/src/main/java/org/apache/sshd/common/util/threads/ThreadUtils.java
@@ -163,9 +163,8 @@
 
         public SshdThreadFactory(String name) {
             SecurityManager s = System.getSecurityManager();
-            ThreadGroup parentGroup = (s != null) ? s.getThreadGroup() : Thread.currentThread().getThreadGroup();
+            group = (s != null) ? s.getThreadGroup() : Thread.currentThread().getThreadGroup();
             String effectiveName = name.replace(' ', '-');
-            group = new ThreadGroup(parentGroup, "sshd-" + effectiveName + "-group");
             namePrefix = "sshd-" + effectiveName + "-thread-";
         }