encoding

Tabular ML is won on features, and this question checks whether you handle the practical traps: target leakage in encodings, missingness that is informative, and fitting transforms on the wrong data. The signal is leakage-safe preprocessing. Here is the toolkit.

base64, leetspeak, invisible Unicode, and foreign scripts all let a payload read as gibberish to your filter but as a clear instruction to the model. The signal is knowing why the model decodes what the classifier cannot.