A phone going into SOS mode is generally a sign of dodgy reception or a telco outage.
But in some cases, it can be something far more sinister.
Phone porting is one of the ways in which scammers and cybercriminals can steal someone's identity, break into their bank accounts and other online profiles – and in some cases make off with thousands of dollars.
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The scary part is, there's not that much you can do to stop it from happening in the first place.
This is what you need to know about phone porting, and what you can do to protect yourself from it.
What is mobile phone porting fraud?
A phone porting hack is when a fraudster is able to have your mobile number transferred from your device to one they control.
According to IDCare, an Australian and New Zealand cybersecurity charity, this generally happens in one of two ways: unauthorised porting and an unauthorised SIM card swap.
Mobile number porting is a completely legitimate service that many of us have used – it allows someone to change telco providers while retaining the same phone number.
However, unauthorised mobile porting takes place "when a criminal contacts a different telephone provider, sets up an account with them and requests to have your number brought over from your current provider," IDCare says.
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A SIM swap is similar, but instead involves the fraudster requesting the activation of a new SIM card using your number.
Many of us use mobile numbers as a form of added security (or two- or multi-factor authentication) for accounts like online banking, emails and social media accounts – for example, entering a code that was texted to you to log in somewhere, or using a text prompt to help with a password reset.
However, when scammers get control of your number and start receiving all calls and texts sent to it, it means they can access those accounts that use the number for two-factor authentication.
This can lead to them gaining control of bank accounts and being able to transfer all the funds into an account of their own.
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What are the warning signs of a porting hack?
The main warning sign actually happens after the port has happened: your phone will lose service, and go into "SOS mode", telling you only emergency calls are available.
In some cases, you might get a text from your telco saying you've requested for your number to be ported to a different network.
If you ever get one of those texts unexpectedly, it's crucial that you contact your provider immediately.
Unexpected emails welcoming you to a new telco, notifications of account logins on new devices, and getting locked out of some of your profiles are other red flags indicating you may have been targetted.
If you get any of those warning signs, or otherwise suspect you've fallen victim to unauthorised porting, get in touch with your telco and bank as soon as you possibly can.
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What can I do to stop unauthorised mobile phone porting?
One of the problems with this kind of fraud is that, because porting is a legitimate service that lots of people use, telcos have had to make it fairly easy to do, and so not that much information is required to port a number – often it's just your name, number and date of birth.
This information can be stolen through phishing scams, so it's important to avoid clicking on any suspicious links and entering personal information into sites you don't recognise.
However, because that information can be relatively easy for criminals to find – sometimes on social media, or in discarded mail – there are some other steps worth taking to mitigate the impacts of having your number ported.
These include using something other than your mobile number as a two-factor authentication method – such as an authenticator app – so that someone won't be able to access your account even if they receive your text messages.
Requesting your telco to put a PIN on your account can help prevent unauthorised porting and using a variety of strong passwords on different accounts can make it more difficult for scammers to get in.
IDCare says using a banking app – with the appropriate multi-factor authentication set up – can also save you some trouble.
"Consider downloading your banking app onto your mobile device," it says.
"Most banking apps provide the ability to temporarily freeze your accounts and cards."
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