Security is one of the most important issues in E-government projects. E-government applications will be increasingly used by the citizens of many countries to access a set of services. Currently, the use of the E-government applications arises many challenges; one of these challenges is the security issues. E-government applications security is a very important characteristic that should be taken into account. This paper makes an analysis over the security as required for E-government and specify the risks and challenges that faces E-government projects in Sudan. Finally, the study has proposed security model for Sudanese E-government. The proposed security model for the Sudanese electronic government is a four layers' model that is divided into sub layers. Each layer will mitigate group of threats related to an e-services. The model is not generic; it cannot be applied by other countries. It is precisely designed for Sudanese situation.