unsupervised learning approach for such task? You may, instead of that, apply supervised learning technique, where you can easily evaluate the performance of the resulting predictive model.
If infrastructure is not an issue here then you can incorporate Neural Networks which will eventually learn the representation of your data and cluster them accordingly. If the size of the data is of higher dimensional then also Neural Networks comes into your rescue.
Read more here: https://pdfs.semanticscholar.org/049e/a1e5bffdd7a494cdc6f560ef56c5a9aee2fa.pdf
If you plan to extend your work to Hadoop ecosystem then also you can apply Neural Networks with map-reduce.
Niloy Chakraborty There is no single or straight forward answer for the question....If you are looking at technique applicable for unlabelled datasets, unsupervised algorithms are the better choice. But then, which algorithm suits well depends on the choice of data used for anomaly detection. This highly releies on the context for which the Anomaly detectors were built...