France's national cybersecurity agency has discovered a hack of several organisations that bore similarities to other attacks by a group linked to Russian intelligence.

On Monday the agency said the hackers had taken advantage of a vulnerability in monitoring software sold by French group Centreon, which lists blue-chip French companies as clients, such as power group EDF, defence group Thales, or oil and gas giant Total. 

The French ministry of justice and authorities of cities such as Bordeaux are also named as Centreon customers on the group's website, but they did not appear to have been compromised, according to a statement on the incident.

"This campaign mostly affected information technology providers, especially web-hosting providers," said the French National Agency for the Security of Information Systems (ANSSI) in a report.

ANSSI had discovered "a backdoor" on several Centreon servers which had given the hackers access to its networks.

"This campaign bears several similarities with previous campaigns attributed to the intrusion set named Sandworm," said the report, referring to a group of hackers thought to have links with Russian military intelligence.

The report, entitled "Sandworm Intrusion Set Campaign Targeting Centreon Systems", was released on Monday and gave technical details about how the hackers gained access to the Centreon servers. 

The attack "recalls methods already used by the Sandworm group linked to Russian intelligence, but it doesn't guarantee that it's them", Gerome Billois, a cybersecurity expert at the IT security firm Wavestone, told AFP.

The hacking took place from 2017 to 2020, ANSSI added.