Belgian has telecommunications group Belgacom found unauthorised changes made to a router at its BICS subsidiary, which provides wholesale communication services to hundreds of operators worldwide.
The changes to the router's software were discovered during a security review of the company's systems launched by Belgacom in September following an intrusion into its corporate network.
"These thorough screenings have divulged some irregularities on a router at BICS, the daughter company of Belgacom and a provider of international carrier services," a BICS spokeswoman said Friday via email.
An investigation found changes to the router software that most likely resulted from the intrusion reported in September, she said. The spokeswoman declined to say if the affected equipment was routing customer traffic or what the identified changes did.
"As the investigation is still ongoing and in the light of the judicial investigation, we cannot comment further at this point in time," she said.
"In collaboration with external experts and in consultation with the investigators, our specialists are preparing the necessary remediation actions," Belgacom said in an emailed statement.
The company shared the information available so far with authorities involved in the judicial investigation and informed the Belgian Institute for Postal services and Telecommunications (BIPT) and the Belgian Commission for the Protection of Privacy.
On 16 September, Belgacom announced it had discovered a previously unknown virus on some of its internal systems. However, at the time the company said that customer data and the delivery of telecommunication services hadn't been compromised as a result of the incident.
A few days later, German news magazine Der Spiegel reported, based on documents leaked by former US National Security Agency contractor Edward Snowden, that the UK's Government Communications Headquarters (GCHQ) intelligence agency was responsible for the attack on Belgacom as part of a project code-named "Operation Socialist."
An undated GCHQ presentation marked top secret indicated that the agency had access to Belgacom systems since 2010 and that its goal had been to compromise the computers of key employees with access to important parts of Belgacom's infrastructure, Der Spiegel reported.
According to the German magazine, the leaked document suggested that GCHQ was on the verge of gaining access to Belgacom's central roaming router that was being used to process international traffic, with the intention of using it for man-in-the-middle attacks on smartphone users. The presentation also indicated that BICS was among the agency's targets, Der Spiegel said.
BICS' network includes over 500 direct connections with over 160 countries and is used to route voice and data communications for more than 700 wired and wireless operators worldwide. The company's carrier services include voice, SMS and roaming.
The European Parliament's Civil Liberties, Justice and Home Affairs Committee held an inquiry into the Belgacom intrusion at the beginning of October.
During that hearing, Belgacom Vice President Geert Standaert, declined to confirm or deny allegations made in the press about the origin of the attack. However, he described the malware that was used as "highly developed software."
Dirk Lybaert, Belgacom's secretary general said during the same hearing that the intruder had "massive resources, sophisticated means and a steadfast intent to break into our network."
Belgacom's customers include the European Commission, the European Parliament and the European Council.