# One class classification with LIBSVM in Weka

I have a dataset on a particular domain and I want to do a one-class classification with LIBSVM (wrapper) in Weka. I have trained the classifier, but the problem is, when I test it with a different dataset than the test set, I get all of them as correctly classified (which I know they are topically different from the training data so no way of correctly classifying). I experimented changing the gamma and the $\nu$ parameter but I can't make a reliable model.

What could be the reason for this?

I would not use SVM's for one-class-classification problems (especially for text), due to their "magic parameters" that are only hard to be interpreted (e.g., the well-known $C$ parameter problem).