Experts at Cybereason discovered that China-linked hackers have breached numerous telco providers controlling their networks. Operation Soft Cell has been active since at least 2012, though some evidence suggests even earlier activity by the threat actor against telecommunications providers. Attackers exfiltrated gigabytes of data from the target networks, but always in relatively smaller amounts to remain under the radar. Hundreds of millions of mobile phone users around the world have been affected, including foreign intelligence agents, politicians, opposition candidates for espionage.”]
Source: https://securityaffairs.co/wordpress/87599/hacking/operation-soft-cell-telco-hack.html