SIM maker Gemalto confirmed that unknown hackers targeted its systems in the period indicated by Snowden, but denied any massive theft of encryption keys. The company confirmed that transfers of sensitive data ware operated through a secure channel. The attacks only impacted its office networks and systems that are not used to manage the SIM encryption keys, but the company clarified that the attackers goal was to steal encryption keys as they were exchanged between GemAlto and its customers. In the case of an eventual key theft, the intelligence services would only be able to spy on communications on second generation 2G mobile networks”]
Source: https://securityaffairs.co/wordpress/34154/intelligence/gemalto-confirms-cyber-attacks.html