It seems my GT 7.7 was hit by some kind of malware, how to check and remove?

[Guest olivex]

The symptom is, each time I switch on my tablet, I receive a notification in lower right corner promoting something like lucky draw, game, etc. If I click on the notification, it automatically starts downloading apk. The apk is always named like yyyymmddxxxxxxxxxxx.apk. I never run those apks, I guess they are not friendly. How can I check which app I installed is doing this?