Adequate system security is the first step towards data integrity and protection, however even with the most advanced protection, modern computer and communication infrastructures are susceptible to various types of attacks. With traditional signature based systems losing proficiency, the Hybrid Intrusion Detection System (HIDS) approach proves the vitality of detecting intrusions and anomalies, simultaneously, by automated data mining over network traffic and signature generation. This paper will focus on analyzing different anomaly detection techniques used to detect zero day attacks and an automatic attack signature generation mechanism that can be complemented with the former. This will serve to be an elemental analysis of a few techniques, their working, and their pros and cons put together in a concise form.