Belgacom (now Proximus) suffered a malware-based attack in September 2013. Belgian newspaper De Standaard reported that investigators had found proof that the hack was the work of the GCHQ, an intelligence service of ally Great Britain. The newspaper added that British Home Office refused to co-operate with the investigation. The attack between 2000 and early 2010, the hackers targeted company admins with spear-phishing attacks aimed at infecting their machines. By installing the malware on engineers computers, the spies had gained control of their machines, and were able to exploit the broad access the engineers had into the networks for surveillance purposes.”]
Source: https://securityaffairs.co/wordpress/77430/intelligence/gchq-hacked-belgacom.html