The attackers claim to have stolen about 5TB of data from the energy giant which was first set up as a public company in 1962 and then taken private three decades later, according to Wikipedia.
Italy's government is still the main shareholder in the company with 23.6% of the shares as of 1 April 2016.
Enel is said to be the 89th biggest global company measured by revenue; it recorded revenue of US$89 billion (A$124.8 billion) in 2019. It is also the second biggest power company after the State Grid Corporation of China.
Ransomware groups have added distributed denial of service attacks to their arsenal in recent times, in order to add pressure on their victims to pay up.
Beginning at the end of 2019, some of the groups rapidly adopted a new feature of exfiltrating data from any attacked site before the encrypting of files began. This means that any attack also involves a data breach.
The exfiltrated data is then used to squeeze a victim, being released on the ransomware group's website in drips and drabs if the victim refuses to pay up.
After a while, the data is also posted to dark web forums frequented by cyber criminals for use as they wish.
This year, NetWalker has been involved in nine incidents that were deemed worthy of being reported.
These included attacks on Indiana-based KYB Corporation, the biggest supplier of OEM automotive equipment to companies around the globe, data centre giant Equinix, US security software-as-a-service provider Cygilant, Australian workforce design and delivery firm Tandem Corp, and Jands, an Australian company that distributes some leading audio, lighting and staging brands for installation, production and retail industries throughout Australia and New Zealand.
Another attack of note was on Forsee Power, a company that designs and manufactures smart lithium-ion battery systems for electro-mobility markets, with a seventh being on Trinity Metro, a regional transportation authority of the state of Texas.
Prior to that the University of California in San Francisco admitted it paid US$1.14 million to a gang that used NetWalker to attack its systems. A ninth case was that of Australian customer experience firm Stellar, that also operates across Asia, North America and Africa.