Python Machine Learning classifier for just one label
The lack of negative examples does not make this unary classification; there is no such modelling, as one-class has no discrimination, and therefore derives no new information from the data set.
As you've pointed out, there are two classes: Legitimate and not.  That's binary.  Use any binary classifier from your research that's capable of deriving boundaries from positive data only.  For instance, so-called "one-class" SVM is one such classifier.
I'm new to machine learning and looking to do run a training / testing dataset through a few classifiers, but the problem I'm having is that I only have one label for my data (Legitimate, currently set as an int so 1 for legit, 0 for not). Ideally I'm looking for a classifier that is going to run with just one label and either confirm or deny if something falls into that label, without the need to specify a second label or class.
Any help would be greatly appreciated!
Many thanks.