Telecom services provider Idea Cellular and financial services firm Aditya Birla Capital said they were not impacted.
However, a third firm, Ultratech Cement, said there was an attempt “to install malware on some desktop systems”, but that it was blocked by the company’s cyber security systems.
The news was first reported by Economic Times on Friday. The report said the attack started with one of the conglomerate’s overseas subsidiaries.
“Within days the malware found its way into some of the manufacturing and other services companies belonging to the business house,” it said.
According to the report, the attackers wanted to install software that mined cryptocurrencies on computers belonging to the group.
The report also quoted an Aditya Birla Group spokesperson as saying that the attack was contained and that its spread was limited.
Typically, such attacks tend to be benign compared to attacks based on ransomware, where the files on the target computers are encrypted and the owner has to pay money to get access to the files again.
In this case, the hackers did not leak any information from the company, the media report said, quoting the spokesperson.