Need some help, unknown video downloaded.

[Josh Strebie]

I need some help, I had a video that downloaded unknowingly. It was an adult video that was an hour and a half long. Showed up in gallery in downloads. After finding it (not knowing when it downloaded) I deleted it. It may have been on there for a few days. Nothing ever indicated that it downloaded. After deleting, phone turned off next morning and was difficult to turn on.

Any ideas how it got on there?

To get the obvious questions out of the way:
#1- I don't visit those kinds of websites.
#2- Ran various free anti-virus programs with no problems.
#3- Haven't downloaded any 3rd party apps from about the time it came on.

 

[Golfdriver97]

I think the best thing to do would be to factory reset and only load the basic apps for your phone. Monitor for a few days, and slowly add more apps a few at a time.

 

[UJ95x]

What device are you using? Some have a safe mode that would allow you to use the phone with no third party apps, so you can find out if any of your apps was the culprit.

 

[Josh Strebie]

Samsung Galaxy S4, latest updates are applied.

I'm in the process of doing the factory reset but does anyone know of this happening before or heard of it? Seems to be more extreme than simple spam.
None of my accounts on anything, from my phone, seem to be affected.

Here is a hunch, would my phone turning off and having a hard time turning back on the next day (after deleting it) be some sort of "system restore" like on a computer? I know it isn't apply-able to an android system like windows. But could the "malware" wiped itself from my phone? That would seem to be more of a "complex worm type" than simple malware on a computer-system, but is it possible on an Android?

I'm more looking for "answers" than "fixes."

Thanks for your replies