unknown download/malware problem

[AC Question]

i clicked the 'play' icon/button at either putlocker or 123movies/gomovies for a movie hosted at openload server and Firefox downloaded some file with no extension. i went to my downloads folder and it wasn't there and my file manager didn't find anything with that name. where the f--- is the "open containing folder" option??! it was 30 minutes before i realized firefox ignored my change in DL location from earlier and recreated the old location and put it there, both on my external SD card. i put it in a zip file and deleted the original. it's named xmmagTg3, 236 bytes, and while my device notifications and downloads still have a record, it was somehow removed from about:downloads by 16 hours later, but while it was there, it noted it had a "location" of where it was downloaded from of "resource data."

phone has been acting up ever since: being really slow, lagging to execute actions; internal memory fluctuating and not changing when changes are made (it had 0.00 for a while (it usually drops into the low KB or B level when playing video), even tho i cleared cache and other things, far longer than usual, then it jumped up to around 53MB an hour later, then 68.x MB it should've been, then back to 53; later i deleted 86MB of thumbnail data and it took 20 minutes to register; bits of memory are disappearing and today, every change is impossibly in whole numbers: 109MB, 108, 106, 105); i haven't been able to tell if the SD card memory has been similarly crazy, similarly unaccountable, but it does still have decimals.

i started to reinstall AVG, but i realized i have to allow unknown sources, and i feel like that might give this whatever an even worse foothold. i can't sign into anything for security's sake, and i'm worried about even restarting it for what may happen, but i'll have to because i'm at only 13% now and the USB port is broken so i have to take my battery out to charge it. i don't think i have enough to backup or move what's on internal storage, but should i even since the file was on my SD card? i unmounted the card to see if there was any improvement in performance, but i haven't noticed any.

i've got an LG Optimus Exceed 2 with unrooted Android 4.4.2. so advice, ideas, recommendations that i might not have thought of?? what can i do to save both files and data like Tasks, Calendar, and Firefox if i have to do a factory reboot?

 

[Rukbat]

Install AVG with "unknown sources" enabled. and run it. (It will run in the background.) Let it run for 24 hours. (And no, that won't make things worse.)

Now download Malwarebytes Anti-Malware and run it.

After another 24 hours, your phone should be clean again.

Now stop downloading unknown files. Many of them are viruses.

(You do a "factory reboot" every time you turn the phone off - what you mean is a factory reset. And, no, if the virus is installed as a system app, resetting won't get rid of it.)

 

[not-a-fandroid]

i forgot i posted as a guest; had to register.

Install AVG with "unknown sources" enabled. and run it. (It will run in the background.) Let it run for 24 hours. (And no, that won't make things worse.)

Now download Malwarebytes Anti-Malware and run it.

After another 24 hours, your phone should be clean again.

okay, and i've already got Malwarebytes, too, but how will i run them for 24hrs? you mean, just leave them installed? (note: my "phone" is just a mobile browser/"lap"top; i don't have a data/wireless plan, just use wi-fi.)

Now stop downloading unknown files. Many of them are viruses.

is that sarcasm, because i didn't willingly download it; Firefox just did it, despite the fact that they've known this to be a problem for over 3 years -- Firefox for Android downloads malware APKs automatically • mozillaZine Forums | https://bugzilla.mozilla.org/show_bug.cgi?id=849630

EDIT: FOUR YEARS!! [Security] Firefox For Android Can Be Tricked Into Automatically Downloading And Executing Malicious Code

(You do a "factory reboot" every time you turn the phone off - what you mean is a factory reset. And, no, if the virus is installed as a system app, resetting won't get rid of it.)

yes, i meant reset; thanks. #brainfart

how might i tell if it is posing as a system app, or just what it is, what it's doing? (i've got that zip filed copy.)