David Bradbury, chief security officer of the identity management company Okta, said five of the company's clients had fallen victim to hacking groups known as ALPHV and Scattered Spider since August.

Deputy communications minister Teo Nie Ching says it is time for a review of the law, to ensure that the provisions are adequate to address offences, especially cybercrime.

First discovered more than a decade ago, Qakbot is commonly spread through malicious, boobytrapped emails sent to unsuspecting victims.

The site was offline, replaced by a banner which read, 'This website has been siezed' and displaying the logos of German, American, Swiss and Polish law enforcement organisations.

The hackers started leaking data after Medibank – the country's largest health insurer – refused to pay a US$9.7 million (about RM45 million) ransom.

Unlike conventional botnets that rely on predetermined channels to ensure their survival, Glupteba is programmed to find a replacement server in order to keep operating even after being attacked, says Google.

The disappearance comes after a series of high-profile ransomware attacks hit major US businesses this year.