WASHINGTON • China largely abandoned a hacking truce negotiated by former US President Barack Obama as President Donald Trump embarked on a trade war with Beijing last year, according to the cybersecurity firm Crowdstrike Inc.

A slowdown in Chinese hacking following the cybersecurity agreement Obama’s administration secured in 2015 appears to have been reversed, the company said in a report released yesterday that reviewed cyber activity by US adversaries in 2018.

“By 2017, they started coming back and throughout 2018, they were back in full force,” said Adam Meyers, VP of intelligence at Crowdstrike. “They have been very active and we expect to see that continue.”

China’s hacking targets in 2018 included telecommunications systems in the US and Asia, according to Crowdstrike.

Groups linked to Iran and Russia also appeared to target telecommunications, a sector that yields “the most bang for your buck” for hackers due to the large number of users that can be accessed after breaching a single network, Meyers said.

The findings align with concern in the US about telecommunications security as the country transitions to the next generation of mobile networks and the Trump administration seeks to secure so-called 5G technology from foreign intelligence gathering.

The administration has expressed particular concern about the spread of products made by the Chinese firm Huawei Technologies Co Ltd.

Crowdstrike said Iran focused much of its cyber activity on the Middle Eastern and North African countries, while Russia engaged in intelligence collection and information operations worldwide.

North Korea deployed hackers for financial gain and intelligence collection, while China targeted sectors including technology, manufacturing and hospitality, Meyers said. — Bloomberg