Could copper fishing line be used as a security scare tactic?

today while i was on a job, i noticed that there was a hair thin strand of copper wire approximately 10 feet in front of a chain link barbed wire fence, hung in overgrown gr and weeds- about 1 foot off the ground. it ran the entire span of the chain link fence, possibly farther- or maybe this is just a coincidence. the wire was barely visible, and probably very easy to break. i am wondering if this is part of a perimeter security system, or just being used to scare of intruders. or perhaps a fisherman did it because he was bored.