A beginners fear of Android malware
This could be a stupid question and I am most likely over reacting, but as it worries me and people say "there are no stupid questions", here we go.
I am worried about a possible infection concerning an Android device.
I used this Samsung Galaxy A52s, last March I switched to a newer model and it has been idling since that.
I noticed that there was a suspicious file, it also transferred to my new phone when I cloned it after the purchase. But the file was never ran on the newer phone - simply deleted.
It aroused my suspicion because: A local bank has this phone number, let's pretend it is +3584011112222. Every time I pay a bill, they send me a confirmation
message there. Unfortunately some scammers also spoof the number and send malicious messages there, then they all show on the same message chain and one has
to be very careful which is which.
OK, the aforementioned file looked like a voice message, and it had the bank's number on the file name as well.
It was something like : message_3584011112222. , the file extension started with an A. Can't remember if it was AMR or something else.
So, I simply deleted it from my new phone, but then I did something stupid. I opened that old Galaxy A52s that has not been used since March and it hasn't got any security etc. updates in a year or so. I ran the file and it was "empty". Just some sound of someone moving furniture or something, that lasted like 10 seconds.
Then I became paranoid. Why the heck did I do that? Why did I run the suspicious file on my old phone.
I ran a factory reset on the old phone. I also factory resetted my 4G modem, I can't remember if it was connected to that phone at the time or not.
My 4G modem is Huawei 535 with the latest 2.1.0.1 or something firmware. (no new one has been released in a couple of years but according to F-Secure router checker it should be ok).
Now I just can't get if off my mind.
- The file name, it had that phone number in it. And my bank never sends voice messages.
- I suppose it was a malicious file, and can my old phone still be infected by it.
- If it was indeed malicious, can it also infect the 4G modem/router. (what are the odds).
- How likely it is that it ran some rootkit that survives factory reset.
- Or the same with the router, that it survives resetting that.
- I also cloned my new phone to my old after the factory reset using Samsung Smart switch, I was going to use it as a spare phone. What are the odds that something transfered back from that to the new phone. Even after resetting the old.
I can't see anything visible wrong in the modem/router settings, I put all the settings as they should be after the reset.
What is your expert opinion, should I be worried that it was some extremely sophisticated trojan/rootkit and it may still cause issues, like jump from one device to another over the wifi, or should I just forget the whole thing and trust that it is gone after resetting the phone and the modem/router.
I have always been so careful with everything, I can't understand what was I thinking when I ran the damn file on that older phone, but I'm sure I will never repeat that with any device.
I have F-Secure installed on my new phone, it has not reported anything, but I don't know if it can find sophisticated rootkits etc.
I know this may sound ridiculous and over reacting, but hey… I'm not an expert and it worries me.
Should I just forget about it ?