Mobile payments are growing rapidly, expected to reach $90 billion by 2017. There are several methods of mobile payment including payment at point-of-sale using NFC technology or magnetic secure transmission, mobile devices being used as point-of-sale, mobile payment platforms for online payments, independent payment systems for specific companies, and direct carrier billing which charges purchases to users' mobile phone bills. Security is crucial for mobile payments and involves authentication, access control, confidentiality, integrity, non-repudiation and availability using mechanisms like fingerprints, passwords, multi-factor authentication, and SSL/TLS with secure elements. Major challenges to address include malware detection, multi-factor authentication, data breach prevention and fraud detection and protection.