Based　on　the　concept　of　constructive　interference　(CI),　multiuser　interference　(MUI)　has　recently　been　shown　to　be　beneficial　for　communication　secrecy.　A　few　CI-based　secure　precoding　algorithms　have　been　proposed　that　use　both　the　channel　state　information　(CSI)　and　knowledge　of　the　instantaneous　transmit　symbols.　In　this　article,　we　examine　the　CI-based　secure　precoding　problem　with　a　focus　on　smart　eavesdroppers　that　exploit　statistical　information　gleaned　from　the　precoded　data　for　symbol　detection.　Moreover,　the　impact　of　correlation　between　the　main　and　eavesdropper　channels　is　taken　into　account.　We　first　modify　an　existing　CI-based　precoding　scheme　to　better　utilize　the　destructive　impact　of　the　interference.　Then,　we　point　out　the　drawback　of　both　the　existing　and　the　new　modified　CI-based　precoders　when　faced　with　a　smart　eavesdropper.　To　address　this　deficiency,　we　provide　a　general　principle　for　precoder　design　and　then　give　two　specific　design　examples.　Finally,　the　scenario　where　the　eavesdropper＇s　CSI　is　unavailable　is　studied.　Numerical　results　show　that　although　our　modified　CI-based　precoder　can　achieve　a　better　energy-secrecy　trade-off　than　the　existing　approach,　both　have　a　limited　secrecy　benefit.　On　the　contrary,　the　precoders　developed　using　the　new　CI-design　principle　can　achieve　a　much　improved　tradeoff　and　significantly　degrade　the　eavesdropper＇s　performance.