diff --git a/bobek.cabal b/bobek.cabal
index 09e513e..3b9c56c 100644
--- a/bobek.cabal
+++ b/bobek.cabal
@@ -23,6 +23,7 @@ test-suite test
   other-modules:       FakeEnvironment
                      , Source
                      , Destination
+                     , Filter
                      , Message
                      , Mover
                      , ReceiveId
@@ -47,6 +48,8 @@ executable bobek
                      , Destination
                      , Mover
                      , ReceiveId
+                     , Filter
+                     , ScriptFilter
                      , Env
                      , RabbitMqEnv
                      , FileEnv
diff --git a/src/Env.hs b/src/Env.hs
index 51c112d..02de1fd 100644
--- a/src/Env.hs
+++ b/src/Env.hs
@@ -7,6 +7,7 @@ import Source
 import Destination
 import ReceiveId
 import Message
+import Filter
 import Control.Monad.Trans.Reader (ReaderT)
 import Control.Monad.Reader (MonadReader, liftIO, ask, MonadIO, runReaderT)
 
@@ -14,6 +15,7 @@ data Env = MkEnv
   { envPublish :: [Message] -> IO PublishResult
   , envReceive :: IO (Either NoMessageReason Message)
   , envAcknowledge :: [ReceiveId] -> IO ()
+  , envFilterAction :: Message -> IO FilterAction
   }
 
 newtype App a = MkApp {run :: ReaderT Env IO a} deriving (Functor, Applicative, Monad, MonadReader Env, MonadIO)
@@ -31,5 +33,10 @@ instance Source App where
     env <- ask
     liftIO $ (envAcknowledge env) ids
 
+instance Filter App where
+  filterAction msg = do
+    env <- ask
+    liftIO $ (envFilterAction env) msg
+
 runMover :: Env -> IO ()
 runMover = runReaderT (run moveMessages)
diff --git a/src/Filter.hs b/src/Filter.hs
new file mode 100644
index 0000000..0785458
--- /dev/null
+++ b/src/Filter.hs
@@ -0,0 +1,16 @@
+module Filter(Filter(..), FilterAction(..), shouldAck) where
+
+import Message
+
+data FilterAction =
+    Ack
+  | Copy
+  | CopyAndAck
+
+shouldAck :: FilterAction -> Bool
+shouldAck Copy = False
+shouldAck _ = True
+
+class Filter m where
+  filterAction :: Message -> m FilterAction
+
diff --git a/src/Main.hs b/src/Main.hs
index af58df0..ea75b00 100644
--- a/src/Main.hs
+++ b/src/Main.hs
@@ -3,12 +3,14 @@ module Main(main) where
 import Env
 import RabbitMqEnv
 import FileEnv
+import Filter(FilterAction)
 import qualified Message as M
 import Destination
 import Source
 import ReceiveId
 import OptParse
 import Data.Text
+import ScriptFilter
 
 import qualified Network.AMQP as AMQP(fromURI)
 
@@ -18,8 +20,8 @@ import Data.Semigroup ((<>))
 printError :: String -> IO ()
 printError errorMsg = putStrLn $ "Unable to initialize rabbitmq environment: " ++ errorMsg
 
-createEnv :: ([M.Message] -> IO PublishResult) -> ((IO (Either NoMessageReason M.Message)), ([ReceiveId] -> IO ())) -> Env
-createEnv pub (rec, ack) = MkEnv pub rec ack
+createEnv :: (M.Message -> IO FilterAction) -> ([M.Message] -> IO PublishResult) -> ((IO (Either NoMessageReason M.Message)), ([ReceiveId] -> IO ())) -> Env
+createEnv fltr pub (rec, ack) = MkEnv pub rec ack fltr
 
 type PublisherFunction = Either String ([M.Message] -> IO PublishResult)
 type SourceFunctions = Either String (IO (Either NoMessageReason M.Message), [ReceiveId] -> IO ())
@@ -39,4 +41,5 @@ main = do
   opts <- execParser (info optionParser (fullDesc <> progDesc "rabbitmq swiss army knife"))
   maybePublisher <- createDestination (destination opts)
   maybeSource <- createSource (source opts)
-  either printError runMover (createEnv <$> maybePublisher <*> maybeSource)
+  let fltr = maybe defaultFilter scriptFilter (OptParse.filter opts)
+  either printError runMover ((createEnv fltr) <$> maybePublisher <*> maybeSource)
diff --git a/src/Mover.hs b/src/Mover.hs
index 75366e2..46322ca 100644
--- a/src/Mover.hs
+++ b/src/Mover.hs
@@ -1,23 +1,35 @@
+{-# LANGUAGE ScopedTypeVariables #-}
 module Mover(moveMessages) where
 
 import Destination
+import Message
 import Source
 import Message()
+import Filter
 
-import Control.Monad (unless)
+import Control.Monad (unless, void)
 
-moveMessages :: (Source m, Destination m) => m ()
-moveMessages = do
-    stuff
+getMessages :: Source m => m (Either NoMessageReason [Message])
+getMessages = do
+  msg <- receive --todo: should use bulked publish
+  return $ pure <$> msg
 
-stuff :: (Source m, Destination m) => m ()
-stuff = do
-  maybeMessage <- receive
-  case maybeMessage of
-    Left _ -> return ()
-    Right message -> do
-      publishResult <- publish [message]
-      let ackable = succeeded publishResult
-      unless (null ackable) $ acknowledge ackable
-      stuff
+publishAndAckMessages :: forall m.(Source m, Destination m, Filter m) => [Message] -> m ()
+publishAndAckMessages msgs = void $ traverse publishSingleMessage msgs --todo: should use bulked publish
+  where publishSingleMessage :: Message -> m ()
+        publishSingleMessage msg = do
+          publishResult <- publish [msg]
+          needsAck <- shouldAck <$> (filterAction msg)
+          if needsAck then do
+            let ackable = succeeded publishResult
+            unless (null ackable) $ acknowledge ackable
+          else return ()
 
+moveMessages :: (Source m, Destination m, Filter m) => m ()
+moveMessages = do
+  maybeMessages <- getMessages
+  case maybeMessages of
+    Left _ -> return ()
+    Right messages -> do
+      publishAndAckMessages messages
+      moveMessages
diff --git a/src/OptParse.hs b/src/OptParse.hs
index 2c624f5..4310349 100644
--- a/src/OptParse.hs
+++ b/src/OptParse.hs
@@ -18,6 +18,7 @@ newtype Path = MkPath Text deriving(Data.String.IsString, Show)
 data Opts = MkOpts
     { source :: SourceOpts
     , destination :: DestinationOpts
+    , filter :: Maybe FilePath
     } deriving(Show)
 
 data SourceOpts
@@ -34,6 +35,15 @@ optionParser :: Parser Opts
 optionParser = MkOpts
     <$> (srcAmqpOpt <|> srcFileOpt)
     <*> (destAmqpOpt <|> destFileOpt)
+    <*> filterOpt
+
+filterOpt :: Parser (Maybe FilePath)
+filterOpt = (optional $ strOption
+        (   long "filter"
+        <>  short 'f'
+        <>  metavar "SCRIPT"
+        <>  help "Filter script path.")
+        )
 
 srcAmqpOpt :: Parser SourceOpts
 srcAmqpOpt = AmqpSource
diff --git a/test/FakeEnvironment.hs b/test/FakeEnvironment.hs
index 612e0fd..640a92f 100644
--- a/test/FakeEnvironment.hs
+++ b/test/FakeEnvironment.hs
@@ -10,6 +10,7 @@ import Destination
 import Control.Monad.State.Strict (State, execState)
 import Control.Monad.State (MonadState, get, put)
 import Safe(tailSafe, headDef)
+import Filter
 
 runMoveMessages :: Environment -> Environment
 runMoveMessages env = execState (run moveMessages) env
@@ -19,6 +20,7 @@ data Environment = MkEnv {
   , acknowledgedMessages :: [[ReceiveId]]
   , published :: [[Message]]
   , publishResults :: [PublishResult]
+  , filterResults :: [FilterAction]
 }
 
 newtype FakeEnvironment a = MkFakeEnvironment {run :: State Environment a} deriving (Functor, Applicative, Monad, MonadState Environment)
@@ -32,11 +34,19 @@ instance Source FakeEnvironment where
     return (headDef (Left NMREmptyQueue) toRec)
 
   acknowledge ackIds = do
-    env@(MkEnv _ acks _ _) <- get
+    env@(MkEnv _ acks _ _ _) <- get
     put $ env {acknowledgedMessages = acks++[ackIds]}
 
 instance Destination FakeEnvironment where
   publish publishedMessages = do
-    env@(MkEnv _ _ pubed pubRes) <- get
+    env@(MkEnv _ _ pubed pubRes _) <- get
     put $ env {published = pubed++[publishedMessages], publishResults = tailSafe pubRes}
     return $ head pubRes
+
+instance Filter FakeEnvironment where
+  filterAction _ = do
+    oldEnv@(MkEnv _ _ _ _ actions) <- get
+    let newEnv = oldEnv {filterResults = tailSafe actions}
+    put newEnv
+    return (head actions)
+
diff --git a/test/Test.hs b/test/Test.hs
index ec37b1f..08b05c1 100644
--- a/test/Test.hs
+++ b/test/Test.hs
@@ -6,6 +6,7 @@ import FakeEnvironment
 import Message
 import Source
 import Destination
+import Filter
 
 testMessages :: [Message]
 testMessages = (\rid -> (MkMessage (MkReceiveId rid) "routing key" "test message")) <$> [1..100]
@@ -25,18 +26,27 @@ someSucceeds succeededIds = (\rid -> if elem rid succeededIds
                                      then MkPublishResult [] [rid]
                                      else MkPublishResult [rid] []) <$> testIds
 
+bothFilter :: [FilterAction]
+bothFilter = repeat CopyAndAck
+
 main :: IO ()
 main = hspec $ do
   describe "moveMessages" $ do
     it "should send message received from the source" $ do
-      let result = runMoveMessages (MkEnv testMessagesToReceive [] [] publishSuccesses)
-      (published result) `shouldBe` (:[]) <$> testMessages
+      let result = runMoveMessages (MkEnv testMessagesToReceive [] [] publishSuccesses bothFilter)
+      (published result) `shouldBe` pure <$> testMessages
 
     it "should acknowledge published messages" $ do
-      let result = runMoveMessages (MkEnv testMessagesToReceive [] [] publishSuccesses)
-      (acknowledgedMessages result) `shouldBe` (:[]) <$> testIds
+      let result = runMoveMessages (MkEnv testMessagesToReceive [] [] publishSuccesses bothFilter)
+      (acknowledgedMessages result) `shouldBe` pure <$> testIds
 
     it "should acknowledge messages only if publishing succeeds" $ do
       let succeededIds = [MkReceiveId 10, MkReceiveId 20]
-      let result = runMoveMessages (MkEnv testMessagesToReceive [] [] (someSucceeds succeededIds))
-      (acknowledgedMessages result) `shouldBe` ((:[]) <$> succeededIds)
+      let result = runMoveMessages (MkEnv testMessagesToReceive [] [] (someSucceeds succeededIds) bothFilter)
+      (acknowledgedMessages result) `shouldBe` pure <$> succeededIds
+
+    it "should acknowledge messages only if the filter asks for it" $ do
+      let onlyCopy = repeat Copy
+      let result = runMoveMessages (MkEnv testMessagesToReceive [] [] publishSuccesses onlyCopy)
+      (acknowledgedMessages result) `shouldBe` []
+
diff --git a/todo b/todo
index b64e0d0..e87e5d0 100644
--- a/todo
+++ b/todo
@@ -1 +1,2 @@
  - handle exceptions during configmwait
+ - add logging