A lot of them are crappy darra made arms, often used simply to threaten people in snatchings. They can cause the user serious injury.
I'd be surprised if you got 50 rounds without a failure out of one of these.
Awareness and fear are far apart. Be aware of your surroundings. If you see any packages/bags/boxes unattended, just inform someone and move away from the area. You can't let fear consume you.