As many as 500,000 Australian websites were rendered inaccessible for up to 90 minutes on Thursday morning, after Melbourne IT's domain name system servers NetRegistry and TPP Wholesale suffered a cyberattack.

Customers took to forums such as Whirlpool to vent their fury at Melbourne IT for the DNS server outage, far from a first for the ASX-listed company. DNS servers are a critical part of the internet's infrastructure, converting the domain names that are typed in to web browsers or generated by Google searches in to the numerical IP addresses needed for locating them on the underlying network.