How to use NLP to determine the normal words in the text I have a lot of .txt files. I want to train the model which remove bad words from the document(bad word - random sequence of characters). 
For example: bad words - hsA , ubj8 ,t+h ,SSSh ,_^[ ,SVWh ,SSSSSS
normal words : *.exe , copy , write ,write ,ftp.exe
You can probably train a classification model to classify normal words from bad words, using character subsequences as features in the words. For example, exe can be a feature for distinguishing a normal word from a bad word in your case.