The Japanese government is considering allowing the peacetime monitoring of private metadata in a way that does not directly identify individuals, in a bid to bolster its pre-emptive cyberattack defenses, government sources said Sunday.

Data such as messages themselves, in principle, will not be subject to monitoring, amid concerns that the plans to strengthen surveillance against potential cyberattacks could infringe on privacy, the sources said.

Japan's Constitution forbids the violation of the secrecy of any means of communication.

Instead, the government would allow, during normal times, surveillance of changes to information such as amounts of metadata -- accompanying data such as a message's size or the date it was sent -- and IP addresses that identify devices on networks.

The sources said the government has judged that limiting the target information to metadata would be within the scope of the law.

Cyberattacks are often staged via multiple devices, making it useful to regularly monitor changes in data traffic and times information is sent.

The government aims to submit a bill during an extraordinary parliament session in the fall at the earliest to boost the country's "active cyber defense," in which signs of cyberattacks are observed and detected, and if necessary, enable preventative measures such as disrupting enemy servers with computer viruses.

The government is also considering creating a framework to allow it to obtain metadata held by the country's communications firms.

Collection and management of the metadata is planned to be centered at a new organization to be devised by the government's National Center of Incident Readiness and Strategy for Cybersecurity.