Data mining has become one of the key features of many security initiatives developed by the Nigerian government to monitor both mobile and internet activities in the country. Attempts are being made to track the data of the so called “yahoo boys” who are taking advantage of e-commerce system available on the internet to defraud unsuspected victims who are mostly. Some target the telecom companies such as MTN, GLO, AIRTEL, ETISALAT, MULTILINKS, STARCOMMS and VISAFONE to defraud them in terms of free browsing, free international calls and free text messaging. While others target credit card companies to hack into their customers database and steal vital information that could make them buy goods/services through the credit cards. Some even go further to defraud individuals through the use of social media such as facebook, tafoo, myspace, and yahoo chat. Unfortunately, few studies have been conducted on the implication of these criminal activities on national security especially in this era of global terrorism. This study therefore examines the correlation between data mining and internet security in Nigeria, analyse the importance of data mining to Call Pattern in Mobile Telecommunication Networks and evaluate the impact of data mining and fraud detection on unsupervised Neural Networks. The target population for the study consists of two hundred undergraduate students (100 males and 100 females) from Lagos State University, Ojo. Data was analyzed using step wise regression analysis. The research contends that there is a correlation between data mining and fraud detection in unsupervised neural networks in that the former helps in improving security in the country.