Who are the Russian cyber gang Qilin?

Russian cyber criminal group Qilin allegedly launched a ransomware attack on Synnovis, a UK pathology service provider, causing operations and tests to be cancelled at various London hospitals. Known for ransomware-as-a-service, Qilin has previously targeted the Big Issue Group and Yanfeng Automotive Interiors among others. While the UK Government generally refuses to pay ransoms, the afflicted company may choose to do so.