fsecu sfecu fescu efscu sefcu esfcu fsceu sfceu fcseu cfseu scfeu csfeu fecsu efcsu fcesu cfesu ecfsu cefsu secfu escfu scefu csefu ecsfu cesfu fseuc sfeuc fesuc efsuc sefuc esfuc fsuec sfuec fusec ufsec sufec usfec feusc efusc fuesc ufesc eufsc uefsc seufc esufc suefc usefc eusfc uesfc fscue sfcue fcsue cfsue scfue csfue fsuce sfuce fusce ufsce sufce usfce fcuse cfuse fucse ufcse cufse ucfse scufe csufe sucfe uscfe cusfe ucsfe fecus efcus fceus cfeus ecfus cefus feucs efucs fuecs ufecs eufcs uefcs fcues cfues fuces ufces cufes ucfes ecufs ceufs eucfs uecfs cuefs ucefs secuf escuf sceuf cseuf ecsuf cesuf seucf esucf suecf usecf euscf uescf scuef csuef sucef uscef cusef ucsef ecusf ceusf eucsf uecsf cuesf ucesf
Note: these 'words' (valid or invalid) are all the permutations of the word fsecu. These words are obtained by scrambling the letters in fsecu.