As networking has become major innovation driver for the Internet of Things as well as Networks on Chips, the need for effective cryptography in hardware is on a steep rise. Both cost and overall system security are the main challenges in many application scenarios, rather than high throughput. In this work we present area-optimized implementations of the lightweight block cipher SIMON. All presented cores are protected against side channel attacks using threshold implementation, which applies secret sharing of different orders to prevent exploitable leakages. Implementation results show that, on FPGAs, the higher-order protected SIMON core can be smaller than an unprotected AES core at the same security level against classic cryptanalysis. Also, the proposed secure cores consume less than 30 percent the power of any unprotected AES. Security of the proposed cores is validated by provable arguments as well as practical t-test based leakage detection methods. In fact, we show that the first-order protected SIMON core does not have first-order leakage and is secure up to 10 million observations against higher-order attacks. The second-order secure implementation could not be exploited at all with up to 100 million observations.