South Korea is forcing parents to keep track of their kids by tracking their smartphones, with all under-19s required to have a monitoring app on their devices.
All new phones sold to everyone aged 18 and under must have Smart Sheriff - a government-designed app which monitors web activity - or another similar app installed.
The move has prompted a debate about privacy in the traditionally paternalistic country, which was governed by authoritarian despots until 1987.
Smart Sheriff and similar apps alert parents to the browsing behaviour of their children, block access to websites deemed undesirable - a list is being drawn up - and raise the alarm over searches such as "pregnancy", "run away from home", "suicide" and "bullying".
The new rules, introduced by the country's media regulator, is being phased in, as it only applies to newly purchased smartphones. Families will not have to install monitoring apps on old smartphones.
However, AP reported last month that state schools were writing to parents to encourage them to install monitoring apps on their children's phones.
And there is no opt-out, and new phones will not work without a monitoring app installed.
Lawyer Kim Kha Yeun, an opponent of the law who is challenging the new rule, told the BBC: "It is the same as installing a surveillance camera on teenagers' smartphones."
South Koreans come of age at 19, when they are able to vote, drink and smoke.
Boys of 18, though, might be a bit miffed at the new tracking rules: their parents might still be prying into their browsing habits even as they are conscripted for military service, which begins at that age.
The government is also tracking the movements of people in quarantined parts of the country, using smartphone data, in a bid to stop the spread of Middle East Respiratory Syndrome (Mera), which has killed 16 people in South Korea to date.
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