I have seen military installations and signs about restricted areas while hiking and traveling around Korea?

Respect any signs marking a military protection zone (군사보호구역), and don't photograph military installations, checkpoints, or areas near the DMZ where photography is prohibited. Drones are restricted near bases and across much of Seoul. On hikes, stay on marked trails, since some border and mountain areas are off-limits, and when in doubt simply don't photograph and don't enter fenced or signed areas.