The explosive growth of e-commerce in previous years has brought unprecedented convenience and global business scope to online trading and at the same time increased the potential of online transaction fraud. Since cybercriminals exploit the vulnerabilities preprogrammed in the digital payment systems, online commerce platforms are facing mounting pressures to build end-to-end cybersecurity frameworks that are designed to protect valuable consumer information and financial integrity. The current research examines the efficiency of three commonly used cybersecurity frameworks, namely, NIST Cybersecurity Framework, ISO/IEC 27001, and PCI DSS, in averting online transaction fraud in the e-commerce spheres. By analyzing fraud-incidence reports, compliance-assessment records, and published breach case studies, this study discovers the relationships between the maturity of framework implementation and the effectiveness of fraud mitigation. A comparative analysis of three leading e-commerce platforms is also performed to compare the speed of threat detection, accuracy of response, and the level of the success of authentication on transaction levels. The empirical evidence shows that a multi-layered, compliance-based security architecture impacts positively on the likelihood and consequence of online fraud. The paper ends with the recommendation of an adaptive, risk-based model of cybersecurity integration that is unique to the real-time e-commerce environment