Reports of cyber-flashing to British Transport Police (BTP) have almost doubled in a year, although campaigners say the number of women affected “will almost certainly be much higher”. The number of women being sent sexually explicit images by strangers on trains is going “largely unreported” despite a spike in incidents, the new data revealed. But what is cyber-flashing, how can you protect yourself against, and what should you do if you become a victim of it? Here's everything you need to know: What is cyber-flashing? Cyber-flashing is when a person is sent an unsolicited sexual image on their device by a stranger nearby through AirDrop, a file-sharing function on iPhones. Victims – often targeted on trains due to the technology’s short range – said it caused them to feel fearful on public transport. If a person’s AirDrop settings are set to “Everyone”, it means someone outside of their contacts list can request to send them a file. This can be done anonymously, as all that is shown on the receiving device is a preview of the picture and the name of the iPhone sending the file. In 2019, where the victim's gender was recorded by the British Transport Police (BTP), the majority of those targeted (88%) were women. More than half (57%) of those whose ages were taken by officers were aged between 21 and 30. Most of the incidents were recorded in London, but reports were also received at stations in Birmingham, Warwick and Guildford. Just under half (44%) received an unwanted image on London underground services last year, while 40% of incidents were reported at National Rail stations. Is it illegal? Laws around image-based sexual abuse are being reviewed by the Government as part of a potential overhaul looking to bring cyber flashing and other digital trends in line with other sexual offences. The Law Commission will examine existing legislation to ensure it is keeping pace with advancements in technology, but is not due to report back until 2021. Scotland made causing a person to look at a sexual image without their consent an offence in 2010. How can I stop it happening to me? AirDrop works by using a combination of Bluetooth and WiFi, meaning both need to be activated for someone to send or receive an AirDrop. It can only be used to send files between Apple products when users have their settings to accept files from anyone. To stop a stranger from being able to AirDrop a file, Apple users can limit the function to people already stored in their contacts. This comes under Settings, then the General tab and then AirDrop. Under this the options are receiving off, restricted to contacts, or available to everyone. How do I report it? The British Transport Police have said that the best way to tackle cyber flashing is to report it as soon as possible after the event. To contact BTP text 61016 or call 0800 40 50 40.