Hackers had access to 250 networks of government agencies and large companies by penetrating software from IT company SolarWinds.
That is what experts tell
The New York Times
The hack at SolarWinds came to light at the end of last year.
The attackers managed to hide the eavesdropping program in software offered by SolarWinds.
Any company installing this software could then be bugged.
The SolarWinds program was installed by the company's 18,000 customers, but experts at first believed that only limited abuse had been made.
Hackers would have mainly tried to look at American government agencies.
Investigative authorities now say the scale is much larger, causing fears of up to 250 attacks.
More and more companies are discovering that they were also involved in espionage.
SolarWinds also has Dutch customers
A list of the 250 affected parties has not been shared.
Earlier it appeared that American government organizations and Microsoft, among others, had been penetrated by the software.
SolarWinds also has Dutch customers, but none have reported a hack so far.
Experts suspect Russia of the attack, which appears to have been carried out by state hackers.
The country denies being involved.
See also: Why the hack at SolarWinds affects ministries and large companies