In this paper, an overview is provided of computer security threats faced by small businesses. Having identified the threats, the implications for small business owners are described, along with countermeasures that can be adopted to prevent incidents from occurring. The results of the Australian Business Assessment of Computer User Security (ABACUS) survey, commissioned by the Australian Institute of Criminology (AIC), are drawn upon to identify key risks (Challice 2009; Richards 2009). Additional emerging threats relating to wireless internet, cloud computing and spear phishing are also outlined, as well as the risks relating to online fraud.