South Korean officials say North Korea has been trying to hack into their smartphones and has also conducted cyberattacks against the South Korean railway transit system.

International Business Times cites South Korean intelligence officials, saying the attack on cell phones was conducted last year between February and March, by tricking the officials into downloading malware. The hackers were so aggressive that South Korean security experts ultimately discovered malware on 20 percent of government phones.

According to the IBT report, the hackers were able to steal “lists of placed and received calls, as well as text messages” and even tap into phone conversations.

Reuters describes the cyberattack on the railway system as an effort to compromise the email accounts of South Korean railway workers, with the ultimate goal of obtaining the information needed to attack the central railroad control system.

“The move was a step to prepare for cyber terror against the railway transport control system,” said the South Korean National Intelligence Service, without going into details about exactly what North Korea might have been planning to do, if it had been able to crack that system. The NIS said it was able to detect the hacking attempts and shut down the compromised email accounts.

The Yonhap news agency reports an emergency meeting on cybersecurity between the South Korean intelligence service and various government agencies was held on Tuesday.

Yonhap reports South Korean president Park Geun-hye “called on government officials earlier in the day to thoroughly cope with any possible cyberattacks from North Korea and to make efforts for parliamentary endorsement of a bill meant to prevent cyberattacks.”