SINGAPORE - Emeritus Senior Minister Goh Chok Tong was among the 1.5 million patients whose personal particulars were stolen in the cyber attack on SingHealth.

ESM Goh, who was on a holiday in Langkawi, said in a Facebook post late Friday (July 20) that he returned home to the news that he was affected.

"Heck! First thing I learnt upon my return from Langkawi was that my non-medical personal particulars with SingHealth had been stolen.

"Cyber theft is a key risk when going digital. But we cannot stop the digital advance and must strive to build the most secure Smart Nation," he wrote in the post.

The authorities had on Friday announced that hackers had infiltrated the computers of SingHealth, Singapore's largest group of healthcare institutions, in an unprecedented breach of personal data here.

Of the 1.5 million patients affected, 160,000 people, including Prime Minister Lee Hsien Loong and a few ministers, had their outpatient prescriptions stolen as well.

Mr David Koh, chief executive of the Cyber Security Agency of Singapore, said that the attack was a deliberate, targeted and well-planned cyber attack. He ruled out casual hackers and criminal gangs, but refused to be drawn on who might be behind the attacks.

Cyber-security experts contacted by The Straits Times said that given the nature of the attacks, these were likely to be state-organised or sponsored, with just a few key countries such as China, Russia and the United States having the capacity to mount such a sophisticated attack.

Calling the data breach the "most serious" in Singapore, Minister for Communications and Information S. Iswaran said the Smart Nation and Digital Government Group (SNDGG) will "pause" the introduction of new infocomm technology systems.

This is to allow the SNDGG to review the cyber-security measures of government systems, and implement any additional safeguards if necessary, he said.

Mr Iswaran emphasised that Smart Nation projects will still be implemented progressively, and that there are no specific projects that are materially at risk of cessation.

SingHealth will be contacting all patients who visited its specialist outpatient clinics and polyclinics from May 1, 2015, to July 4, 2018, to notify them if their data has been stolen. An SMS message will be sent to all patients over the next five days.

Patients can also access the Health Buddy mobile app and SingHealth website to check if they are affected by the breach. They can also check using this link: https://datacheck.singhealth.com.sg/