Just bought used S7 Edge. Should I...???

[Mariuxas77]

Okay, so I just got second hand S7 edge and I'm a little bit worried since I never bought a used cellphone previously. My concern is: should I factory reset the phone? BecauseI have a paranoia that the person from whom I bought the phone might installed some tracking app that is very difficult to locate like it won't show in installed app list (you could think of it like a virus) and he might track everything I do.

So if that is true which is unlikely but if it is, would factory reset remove that hypothetical spying app or whatever he might have installed? Is there any way I can reset the phone so everything I mean absolutely everything would be deleted and what is left would be basically factory apps with operating system and it's core parts and settings. And nothing more.

One would think it's the seller who should be worried that his data might be recovered but..strange that it's me this time. Sorry, it's just my paranoia combined with conspiracy.

Thanks.

 

[svim]

If you bought the phone from a reputed pre-owned phone seller like swappa.com, or gazelle.com, or whatever than the odds are the phone is 'clean'. That's not an absolute of course but much, much safer than if you bought it from someone just selling phones on craigslist.
In either case, doing a Factory Reset is a recommended step for any pre-owned phone. If you're really worried about security and privacy, you should also just re-flash the stock ROM for your phone. A Factory Reset only clears the user data partition, it does not do anything to the Android operating system. If (and that's a notable 'if') the previous owner did install some kind malware/spyware as root and then un-rooted the phone, a Factory Reset wouldn't fix things since the exploit would probably be buried in one of the system partitions. So flashing the ROM should take care of the problem.
If you want to flash the stock, Samsung ROM, go here:
https://updato.com/firmware-archive-select-model?q=galaxy+s7+edge&exact=1
and pick the ROM that exactly matches your model of S7 Edge. Don't mix and match, choose the one that's specifically for your model. On the actual download page of the ROM you've chosen are instructions on how the flashing process.

It's not likely that anything has been done to that phone you bought, most people just aren't doing anything nefarious to their phones when they pass them on. There are always a few morons out there though, so it while the odds are that phone is fine as is, you might want to invest in the time and effort to set that phone up from scratch.
The first time you started up the phone, did it prompt you to enter a Google account I.D.? A new phone will do that, and a properly prepared used phone will do that. If you weren't prompted to set up the phone to your Google account, that's not a good sign.

 

[Mariuxas77]

Thanks so much for such a detailed and comprehensive reply. To answer your questions, I bought it from random person that I saw an add. My friend picked it up for me because he was at that particular city right that moment. The handset looks in perfect condition though. And still has warranty valid till november. Anyway, I decided to perform factory reset only. The person that I bought the phone from was described by my friend as family man in his late 30's. So I really doubt he did anything to the phone. Even if he did which now seems extremely unlikely, factory reset probably took care of it. Because I looked at the spying apps for androids and most of them need to be reinstalled when you receive an OS update. I really doubt he went all the way to find an app that will be burried in system partition like you said.

Just one thing, when I first started the phone, it did not prompt me to Google account I.D. So my guess would be that the previous owner actually did not factory reset the handset before giving it away and just manually deleted all his files. Which would be the stupidest thing to do before selling a phone. I thought people knew basic stuff like that. I don't know if it's the red flag though. Like it's really not me this time who should be worried. It's more likely that I can restore all his data and might try to steal his sensitive information, not the other way around. Of course I have no interest and intentions like that. Not that level of scum.

Also, not creating another topic, would you be so kind or maybe someone else here and recommend me a good anti-virus for android? Or maybe something similar to anti-virus that would increase security to the max.

Thanks in advance.

 

[svim]

...
Also, not creating another topic, would you be so kind or maybe someone else here and recommend me a good anti-virus for android? Or maybe something similar to anti-virus that would increase security to the max.
Thanks in advance.

https://www.computerworld.com/article/3268904/android/android-security-facts.html
Just my opinion of course but I don't think you should install any kind of anti-virus/anti-malware app. If you're encountering problems than perhaps yes, but for day-to-day usage on a typical Android device, those utilities are just tying up system resources and allegedly 'protecting' you from mostly fabricated and often just theoretical exploits. There's a good argument on being proactive on protecting your device but at the same time there are inherent ways your Android device is already securing itself. A major factor is just don't do stupid things - don't sideload apps from unknown, unverified sources; don't just click on any link someone sends you in an email or text; don't allow just anyone to have unsupervised, physical possession of your device; etc.
The bottom line is even if you do opt to install an anti-virus/anti-malware app on your phone, you'll probably be installing it from the Play Store and being such it will be installed as a user app, that is without system-level privileges. So at that point, its effectiveness is a half-measure since while it will 'protect' your data and things that are stored in the user's general data partition, if some exploit does work its way into your device that effects your device's operating system, that a/v app you installed can't do much to correct the problem since it simply doesn't have the necessary system privileges.