Almost no one still picks up phone calls from unknown numbers, but if you
do, you need to listen closely to what the person on the other end says. If
you receive a call and immediately hear the phrase “Can you hear me?,”
Immediately HANG UP!
The phrase is used to coax you into saying “YES,” a word that, if
said in your voice, is as good as gold for con artists.
Source: Los Angeles Times newspaper