"From today, the remaining patients to be contacted will receive the following SMS with the revised URL", said SingHealth in its Facebook post.
"Study of the cyber security Agency of Singapore Integrated health information system have confirmed that it is deliberate, targeted and well-planned cyber attack", - quotes Agency the statement of the government.
Medical information, such as personal data, can also be easily monetized on criminal forums, Darktrace Asia-Pacific managing director Sanjay Aurora said.
A data breach in Singapore resulted in a quarter of the country's population having their information stolen.
The hackers first broke into SingHealth's IT system via a front-end workstation, and later managed to obtain log-in details to assess the database, according to CSA's investigations.
"It was not the work of casual hackers or criminal gangs", the ministry said, adding that the attackers targeted details about Lee and the medicines he received.
SingHealth's database has experienced a major cyber-attack. Also, none of the diagnoses or test results were stolen, just the personal profiles.
The cyber security Agency of Singapore said that the hackers ' actions were purposeful and well planned. Going digital would enable my doctors to treat me more effectively and in a timely manner.More news: British Open: Francesco Molinari wins Open championship as Tiger Woods falls short
On Friday afternoon, SingHealth announced that the non-medical personal particulars of some 1.5 million patients who visited SingHealth clinics from 1 May 2015 to 4 July 2018 were illegally accessed and copied.
He added: "I don't know what the attackers were hoping to find". A police report was made on July 12. "These include temporarily imposing internet surfing separation" on all of SingHealth 28,000 employees, authorities say.
According to authorities, hackers used a malware-infected computer to gain access to the database at some point between June 27 and July 4, before administrators spotted "unusual activity". "Unfortunately that has now happened". They also have introduced additional controls, reset the user and systems accounts as well as installed more systems for monitoring objective.
Furthermore, additional controls on workstations and servers, reset user and systems accounts and installed additional system monitoring controls, were also enacted. The statement released by the Ministry of Health mentions that the other medical records of the affected people are safe and that none of the record information had been compromised.
State actors were likely behind Singapore's biggest-ever cyberattack to date, security experts said, citing the scale and sophistication of the hack.
No further data has been stolen since July 4.
Even though a thorough review of Smart Nation projects will be conducted, he stressed that Singapore has paused but not halted these projects.