https://www.theregister.co.uk/2019/10/22/eset_sql_server_backdoor/

Security researchers at ESET have published details of a backdoor into Microsoft's SQL Server via hooks and the splendidly named "magic passwords".

The backdoor, which targets SQL Server 2012 and 2014, has the ability to leave a miscreant with stealthy access to a compromised server and forms part of the arsenal of a malware group dubbed "Winnti" by researchers.