An overview over secure communication in massive multiple-input multiple-output (MIMO) systems is presented. A massive MIMO base-station serves multiple user nodes by provisioning physical layer security techniques to secure the confidential transmissions against an eavesdropper. The eavesdropper can either be passively eavesdropping upon the communication or can actively contaminate the channel estimates. The achievable secrecy rates for these settings are reviewed, and their asymptotic behavior is discussed. Finally, a detection scheme for active pilot contamination attacks is discussed.