Symantec has announced that Francis deSouza, the companys president of products and services, will be leaving the IT security giant on December 1. He will become the president of Illumina, a San Diego-based company that specializes in life science research, molecular diagnostics, and genomics. deSouza joined Symantec back in 2006 when the company acquired IMlogic, a firm he had co-founded. After his departure, Symantecs products and services leade…