Political activists living under oppressive regimes, and journalists reporting from the front line, are among those who fear being kidnapped and tortured.
And while little can be done to abolish this threat entirely, a new app has been launched that turns an ordinary smartphone into a discreet panic button.
The Panic Button app is designed to give people defending human rights in dire situations urgent help from their own network if they are attacked or kidnapped.
Launched by Amnesty International, it is designed for Android smartphones and is available to download from Google's Playstore.
The app transforms a smartphone into a secret alarm that can be activated rapidly in the event of an emergency, alerting fellow activists to the danger their colleague faces so that they can get help faster.