diff --git a/modules/system/system.api.php b/modules/system/system.api.php
index 195bc83..ab7d500 100644
--- a/modules/system/system.api.php
+++ b/modules/system/system.api.php
@@ -2302,7 +2302,7 @@ function hook_theme_registry_alter(&$theme_registry) {
  * @return
  *   The machine-readable name of the theme that should be used for the current
  *   page request. The value returned from this function will only have an
- *   effect if it corresponds to a currently-active theme on the site. Do not 
+ *   effect if it corresponds to a currently-active theme on the site. Do not
  *   return a value if you do not wish to set a custom theme.
  */
 function hook_custom_theme() {
@@ -2826,7 +2826,15 @@ function hook_file_insert($file) {
  * @see file_save()
  */
 function hook_file_update($file) {
-
+  $file_user = user_load($file->uid);
+  // Make sure that the file name starts with the owner's user name.
+  if (strpos($file->filename, $file_user->name) !== 0) {
+    $old_filename = $file->filename;
+    $file->filename = $file_user->name . '_' . $file->filename;
+    $file->save();
+
+    watchdog('file', t('%source has been renamed to %destination', array('%source' => $old_filename, '%destination' => $file->filename)));
+  }
 }
 
 /**
@@ -2840,7 +2848,14 @@ function hook_file_update($file) {
  * @see file_copy()
  */
 function hook_file_copy($file, $source) {
+  $file_user = user_load($file->uid);
+  // Make sure that the file name starts with the owner's user name.
+  if (strpos($file->filename, $file_user->name) !== 0) {
+    $file->filename = $file_user->name . '_' . $file->filename;
+    $file->save();
 
+    watchdog('file', t('Copied file %source has been renamed to %destination', array('%source' => $source->filename, '%destination' => $file->filename)));
+  }
 }
 
 /**
@@ -2854,7 +2869,14 @@ function hook_file_copy($file, $source) {
  * @see file_move()
  */
 function hook_file_move($file, $source) {
+  $file_user = user_load($file->uid);
+  // Make sure that the file name starts with the owner's user name.
+  if (strpos($file->filename, $file_user->name) !== 0) {
+    $file->filename = $file_user->name . '_' . $file->filename;
+    $file->save();
 
+    watchdog('file', t('Moved file %source has been renamed to %destination', array('%source' => $source->filename, '%destination' => $file->filename)));
+  }
 }
 
 /**
@@ -3638,7 +3660,7 @@ function hook_registry_files_alter(&$files, $modules) {
  * inspect later. It is important to remove any temporary variables using
  * variable_del() before your last task has completed and control is handed
  * back to the installer.
- * 
+ *
  * @param array $install_state
  *   An array of information about the current installation state.
  *