diff --git a/lib/strategy/mongodb/blacklist.rb b/lib/strategy/mongodb/blacklist.rb
index 4160dd9..1591354 100644
--- a/lib/strategy/mongodb/blacklist.rb
+++ b/lib/strategy/mongodb/blacklist.rb
@@ -2,25 +2,57 @@ module DataAnon
   module Strategy
     module MongoDB
       class Blacklist < DataAnon::Strategy::MongoDB::Whitelist
-
         def self.whitelist?
           false
         end
 
-        def process_record index, document
-          anonymized_document = anonymize_document(document, index, @fields)
-          source_collection.find({'_id' => anonymized_document['_id']}).update_one(anonymized_document)
+        def process_record(index, document)
+          id = document["_id"]
+          begin
+            anonymized_document = anonymize_document(document, index, @fields)
+            updates = flatten_for_update anonymized_document
+            # skip empty documents/updates
+            if ((updates.kind_of?(Array) || updates.kind_of?(Hash)) && updates.size == 0)
+              return;
+            end
+            # differential mongodb update via { $set: { 'doc.nested.array.0.attr': 'value' }}
+            source_collection.update_one({ "_id" => id }, { "$set" => updates })
+          rescue StandardError => e
+            puts e.message
+          end
         end
 
-        def anonymize_document document, index, field_strategies = {}
+        def anonymize_document(document, index, field_strategies = {})
+          anonymized_document = {}
           field_strategies.each do |field_name, field_strategy|
             field_value = document[field_name]
             unless field_value.nil?
               field = DataAnon::Core::Field.new(field_name, field_value, index, document, @name)
-              document[field.name] = AnonymizeField.new(field, field_strategy, self).anonymize
+              result = AnonymizeField.new(field, field_strategy, self).anonymize
+              if !((result.kind_of?(Array) || result.kind_of?(Hash)) && result.size == 0)
+                anonymized_document[field.name] = result
+              end
+            end
+          end
+          anonymized_document
+        end
+
+        def flatten_for_update(object, level = 0, name = "", updates = {})
+          path = name.to_s
+          if object.is_a?(Array)
+            if level > 0
+              path += "."
+            end
+            object.each_with_index { |child, idx| flatten_for_update(child, level + 1, path + idx.to_s, updates) }
+          elsif object.is_a?(Hash)
+            if level > 0
+              path += "."
             end
+            object.each { |key, value| flatten_for_update(value, level + 1, path + key, updates) }
+          else
+            updates[path] = object.inspect
           end
-          document
+          updates
         end
 
       end