An unusually high amount of traffic to many Government sites was observed on Nov 5 - the day which hacktivists called for Singaporeans to mount a virtual protest against new Internet regulations.

This was indicative of attempts to scan for vulnerabilities or potential of a distributed denial of service (DDoS) attack, the Infocomm Development Authority (IDA) revealed in a press conference on Friday afternoon.

In view of the threats made last week, Government agencies were put on heightened vigilance after being warned of the possible Nov 5 attack. Despite this, two pages that allowed the public to search the Prime Minister's Office (PMO) and Istana websites were compromised late on Thursday at 11.17pm and early Friday at 12.20am respectively.

The IDA explained that this was done by targeting a vulnerability in the Google search bar within the sites. The IDA added that both the PMO and the Istana websites are still functioning, even as restoration of the affected pages are underway. The matter is also being investigated by the police, it added.

"We will continue to strengthen all Government websites. This includes the checking and fixing of vulnerabilities and software patching. While this is in progress, visitors to Government websites may experience intermittent problems with access," the statement said.

On Wednesday, Prime Minister Lee Hsien Loong said that the authorities will "spare no effort" to track down those who threaten to attack the country's computer networks and bring them to justice.

It was his first comment since hackers last week threatened to hit out at Singapore's information technology infrastructure in a show of protest against new licensing rules for news websites.