Belgacom, the largest telecoms company in Belgium, has performed a system wide clean up and tightening of security following a cyber attack the country's government - Belgacom's main shareholder - suspects to be an international espionage attempt.
In a statement, Belgian Prime Minister Elio di Rupo said that the attack appeared to be a "strategic information gathering" effort, rather than an instance of cybercrime, with the technology used suggesting "a high-level involvement by another country".
Rupo has declined to say which country he suspects. Belgacom has said only that it "filed a complaint against an unknown third party" and it is for the the Federal Prosecutor's ongoing investigation to clarify who was the perpetrator.
Reports from within the country however suggest that the NSA was behind the attack, with De Standaard writing that evidence has been found that the US agency has been hacking Belgacom since 2011, to access international communications that pass through the network.
In a statement, Belgacom said that its security experts had found "an unknown virus in a number of units in our internal IT-system".
Making clear that the company and government knew nothing of the data collection, it added that "Belgacom strongly condemns the intrusion of which it has become a victim."
"This weekend, Belgacom successfully performed an operation in the light of its continuous action plan to protect the security of its customers and their data and to assure the continuity of its services," the company said.
"For Belgacom, the protection of the customers and their data is a key priority. At this stage there is no indication of any impact on the customers or their data. At no point in time has the delivery of our telecommunication services been compromised."