Next generation mobile networks and services are gaining market momentum every day. Service providers are seeking new ways to generate revenue and this is usually achieved by designing new downloadable applications that take advantage of the advanced handset technology and the higher per user bandwidth. It is therefore an ongoing challenge to protect against attackers and malicious code writers who attempt to obtain services for free. In most cases these applications are written in object oriented, class based languages such as Java or application platforms like .net. This paper will analyse the vulnerabilities of such application software. Analysis will mainly focus on vulnerabilities inherent in such languages regardless of the methods the application designers may choose to protect them. It is assumed that application protection mechanisms are secure. Methods are going to be suggested to prevent these attacks and make application protection more effective.