This is an exact description of the panic feature built into phones as Peter Harmann already said.
Anecdotally I can tell you on my previous Samsung smartphone, I could trigger this exact feature by pressing the power button 3 times in a quick succession. My phone would then take a couple pictures record a short clip of audio and then text those along with my current gps location to a list of contacts I had set up previously. This could actually be incredibly useful as a panic feature to get help when you are in so much danger that you can't otherwise call/text for help.
I'll address your questions a little more specifically:
- I am right assuming this is only Hellen's problem and as long as
Jane ignored and deleted her messages she is safe?
If this was an actual emergency for Hellen, you absolutely should not ignore her cries for help. If this was some sort of virus, then it could take advantage in one of two ways:
- It sent you a link you need to click on. (Obviously, not clicking it is the correct action and you'll be fine if you don't click it. Just delete the messages so you don't accidentally click it in the future.)
- It sent you a text that is able to exploit your messenger app in some way. Like the single-character messages that crashed iPhones. In that case, you are compromised just by opening the text. Proceed assuming you have been compromised.
- How should we proceed about Hellen's phone? A simple factory reset would do it?
If this was a virus text, it could have come in multiple ways.
- Hellen's phone is indeed compromised. A factory reset might do it. Or it might not. Malware can be very hard to get off a machine once it has its hooks deep inside.
- The attacker didn't compromise Hellen's phone, they just spoofed her number to call/text their victims.
- The attacker impersonated Hellen in order to steal her number. Hellen's phone is fine (except that it no longer works as a phone because her number is stolen).
- How can we prevent this situation in the future?
Hellen can turn off her panic feature or take you off the texting list.
As for malware texts, there's not much you can do about your friends getting hacked except educating them or getting different friends.
What should you do if you get a text like this?
First, try to call your friend. They might actually be in trouble. Or they might be fine and it was just a mistake. Or it might be malware. Now you both know and can deal with it accordingly.
Second, they might not be able to answer you because of their emergency. Still don't click any links, but do call the authorities or other people who could help. Especially if the pictures or audio indicates they are in serious danger.
Third, if it is an emergency, you might need that information from the link (i.e. their location on google maps). You can type in the link manually if it looks like its a trustworthy destination (i.e. google maps). Or if this is time critical and you've confirmed this is an emergency, you might just have to bite the bullet and click the link.