After introducing a nightly nudge to encourage teens to stop using Instagram at night, Meta is now introducing additional messaging settings to keep them safe online. Under these 'Stricter Private Message Settings for Teens', teens will by default not be able to receive direct messages from users they don't follow or have a connection with, such as via Facebook or their phone contacts.
Instagram Safety Measures for Teens: A Closer Look at Stricter Posting Limits and Defaults
Teens can only receive messages or be added to group chats by people they're already in contact with. This is in line with the new default setting that applies to all teens under 16 (or 18 in some countries).
Users will be notified of the new change in notification settings as shown below.
Additionally, Meta will alert parents who use Instagram's parental control tools when their teens want to change their default privacy settings and make them more lenient.