South Korean arms makers tell staff to carry rented phones on trips to China

South Korean defence contractors are tightening security for employees who travel to China, with at least one company telling staff to leave their own smartphones at home and carry rented devices instead, Yonhap News Agency reported on Sunday 25 October, citing the industry. The Seoul Economic Daily reported the same guidance later that day, attributing it to defence industry sources.

According to both reports, the guidance covers visits to China and other countries with strict cyber surveillance, and it applies to holidays as well as business trips. The worry is that work information held on a phone could be exposed through an inspection by local authorities, through hacking, or through loss or theft. Staff who cannot avoid taking a personal phone were told to delete work applications and important files before they leave.

The same company also told employees not to use public Wi-Fi networks or USB charging ports at airports and hotels, saying that data theft and malware infections through them had been reported repeatedly. Neither outlet named the companies that issued the instructions.

A second contractor has advised staff to avoid flights that transit through China when travelling on business, Yonhap said, and a third has run security training for employees going abroad since 2024. That course covers mobile device security, what to do if a phone is seized or the traveller is detained, and how to resist social engineering, in which attackers exploit trust or personal psychology to draw out information.

The firms are responding mainly to China's new State Council regulations on exit and entry administration, which took effect on 15 September. Under the rules, officials checking a traveller's identity and reason for a visit may ask for electronic data as well as paper documents, and travellers are required to cooperate. Foreigners penalised for submitting false material or for illegal entry or exit can be refused entry for a set period. The immigration consultancy Newland Chase, in a note issued when the decree was published in August, described entry bans of one to five years.

A rise in leaks of defence material has added to the concern. Figures that the Defense Acquisition Program Administration gave to Yoo Yong-won, a People Power Party member of the National Assembly's defence committee, show 62 leaks at defence companies and their suppliers between 2021 and 1 October this year, Yonhap reported. The yearly count was eight in 2021, three in 2022 and five in 2023, before it jumped to 17 in 2024 and 16 in 2025, with 13 more through September 2026.

Those totals differ slightly from an earlier Yonhap report on the same lawmaker's data, published on 13 October, which gave 63 leaks since 2021 and 14 so far this year. Neither report explained the gap, which may reflect different cut-off dates, and TaiwanDefence has not been able to reconcile the two counts.

Most leaks came from outside cyberattacks rather than from staff removing files without permission. The arms agency's data attributed 16 of the 17 cases in 2024 and 14 of the 16 in 2025 to hacking or other attacks. Hacking believed to be linked to North Korea was confirmed in two cases in 2024 and one in 2025, and files were actually taken in two of them. In 15 further cases since 2021, a suspected leak was reported but investigators could not establish whether any data had gone.

The agency has said attackers are hard to trace because they alter their internet addresses and route traffic through servers abroad. It linked the North Korean cases to Pyongyang on the basis of the addresses and methods used. Yonhap reported that people in the industry nonetheless suspect that a considerable share of the attacks may have involved China, a view the agency has not confirmed.

An industry official told Yonhap that awareness of security risks coming from China is widespread among defence workers, and that companies are adding guidance because a lapse by even a small number of employees could lead to a leak. When the figures first emerged, Yoo urged the arms agency to tighten its oversight of defence technology security, arguing that protecting core national technology is directly tied to national security.