You will be receiving a letter if you are affected by the cyber attack or you can check online using your secured SingPass.

https://datacheck.singhealth.com.sg/

Singapore News -At a multi-ministry press conference on Friday, the authorities said PM Lee’s information was “specifically and repeatedly targeted”.. Read more at straitstimes.com.

Source: Personal info of 1.5m SingHealth patients, including PM Lee, stolen in Singapore’s worst cyber attack, Singapore News & Top Stories – The Straits Times