如果你要在表单中需要一个敏感字验证，可以这么写：

/** 
 * implementation of hook_form_alter()
 */
function custom_form_alter(&$form, &$form_state, $form_id) {
  switch ( $form_id ) {
    case 'complaint_node_form':
      $form['#validate'][] = 'custom_badwordsnode_validate';
    break;
    case 'comment_form':
      $form['#validate'][] = 'custom_badwordscomment_validate';
    break;
  }
}

/** 
 * implementation of hook_validate()
 */
function custom_badwordscomment_validate($node, $form) {
  $badWords = taxonomy_get_tree(5);
  $badWordsUsed = array();
  foreach ( $badWords as $badWord ) {
    if ( strpos($form['values']['comment'], $badWord->name ) !== false ) {
      $badWordsUsed['comment'][] = $badWord->name;
    }
  }
  if ( count( $badWordsUsed['comment'] ) > 0 ) {
    form_set_error('comment', t('The fallowing words are not allowed: '. implode('; ', $badWordsUsed['comment']).'.') );
  }
}

/** 
 * implementation of hook_validate()
 */
function custom_badwordsnode_validate($node, $form) {
  $badWords = taxonomy_get_tree(5);
  $badWordsUsed = array();
  foreach ( $badWords as $badWord ) {
    if ( strpos($form['values']['title'], $badWord->name ) !== false ) {
      $badWordsUsed['title'][] = $badWord->name;
    }
    if ( strpos($form['values']['body'], $badWord->name ) !== false ) {
      $badWordsUsed['body'][] = $badWord->name;
    }
  }
  if ( count( $badWordsUsed['body'] ) > 0 ) {
    form_set_error('body', t('The fallowing words are not allowed: '. implode('; ', $badWordsUsed['body']).'.') );
  }
  if ( count( $badWordsUsed['title'] ) > 0 ) {
    form_set_error('title', t('The fallowing words are not allowed: '. implode('; ', $badWordsUsed['title']).'.') );
  }
}

你也可试一下下面两个模块：

phonetic wordfilter，Wordfilter