In a first such instance, a case of "cyber-flashing" has been registered in London after a woman received photographs of a man's penis via iPhone's AirDrop feature. The unpleasant images were shared during her journey on a train in south London, which indicates the stranger sharing indecent pictures was on-board.

The owner of an iPhone must be well-versed with the AirDrop function, which is used to transfer files to another iPhone device within a short range of distance. The 34-year-old woman, identified as Lorraine Crighton-Smith, shared her experience with BBC and the possibilities of cyber-flashing targeting vulnerable victims.

Crighton-Smith reported the incident to the British Transport Police, who are investigating the matter. After the incident took place, Crighton-Smith said she felt "violated" by the picture. Declining the gross images on AirDrop was the immediate and the right thing to do at the time, but that leaves the police with no technological evidence to catch the culprits.

Superintendent Gill Murray recalled solving similar cases with Bluetooth but use of AirDrop is entirely new.

"Receiving an indecent image from someone you don't know must be very distressing and something we would take very seriously. If it happens to you, our advice would be to remain calm, retain the image and report the matter to police as soon as possible," Murray told BBC.

"We have a dedicated Cyber Crime Unit who can analyse mobile phones and track data transfers back to suspects' devices. By linking this to physical evidence, such as CCTV footage or witness statements, we can catch offenders and bring them to justice through the courts," she added.

How To Protect Yourself From Cyber-Flashing?

As the first cyber-flashing incident is related to iPhone's AirDrop feature, users have options to control who can send them images. The default setting for AirDrop is to communicate only with contacts, which means only the people you know can share something with you.

However, AirDrop also has an option to widen the search of audience while receiving files. If you change "Contacts Only" option on AirDrop to "Everyone" anyone within a range can send anything.

"That's what's happened in this particular case, someone has enabled everyone and then hasn't then set it back. As a result anyone within wi-fi or Bluetooth range can send something to you that's quite horrible," Ken Munro, a cybersecurity consultant at Pentest Partners, explained.

It is important that you make sure the setting on your AirDrop is set to default for "Contacts Only" or best to turn it off while not in use. AirDrop is accessible on your iPhone by swiping up from the home screen.