Anyone with an iPhone or Android device tucked in their pockets hould stay vigilant today. The UK government is testing an Emergency Alert system on Sunday which will ring out of every device across the country at 3pm.
Although this warning is simply to put the new technology through its paces in readiness for a real crisis in the future, it could actually put some users in danger.
Experts are warning that the Emergency Alert is the perfect smokescreen for cyber criminals who will use the test to try and trick phone users into handing over personal data.
"Scammers will use any hook they can to try and steal money and personal information from victims, and unfortunately the government's upcoming nationwide test of its new Emergency Alerts system will be no exception," said Lisa Webb, Which? Scams Expert.
"It's vital anyone who receives the official test alert is aware that no action is required. If you are asked to download an app or provide information, this is likely to be an unscrupulous fraudster trying to trick you and should be ignored at all costs.
"The government has said it will be including a website link with more information about the alerts in the message it sends out, but it's worth considering looking this information up separately through the official government website rather than risking clicking on lookalike links from fraudsters.
"People can report any scam calls or texts they receive to 7726. If you or a loved one do fall victim to a scam then contact your bank immediately and report it to Action Fraud."
The real test, which will arrive on all iPhone and Android devices unless switched off in the settings, will belt out a loud alert siren and then take over the whole display with a message.
The government has confirmed that the alert will read: "This is a test of Emergency Alerts, a new UK government service that will warn you if there’s a life-threatening emergency nearby. In an actual emergency, follow the instructions in the alert to keep yourself and others safe. Visit gov.uk/alerts for more information. This is a test. You do not need to take any action."
An "OK" button can then be tapped to take the device back to the usual home screen.
If you don't want to take part in the test you can switch it off in the settings menu on your phone or simply turn off the device at 2:59pm.
To turn off the alerts on iPhone go to Settings > Notifications > Then scroll to the bottom of the list and toggle off Extreme Alerts and Serve Alerts.
On Android simply search your settings for emergency alerts using the search icon. From the results, turn off severe and emergency alerts.
If you leave it on, just beware of cyber thieves trying to trick you.