Problems with downloaded Tubemate

[Challenged_101]

I downloaded Tubemate directly from the Softonic website and upon running, am getting a pop-up warning, virus detected, remove now. I have a ATT Galaxy S3 with 4.1.1 running stock rom. I haven't installed any anti-virus so do I assume this is some kind of malware - scareware or is there a stock anti-virus program on this phone. Softonic claims it's virus free, and I've downloaded it also to the laptop and it scanned clean.
Tubemate isn't available from the Play Store and it couldn't get it to download from AndroidFreeware. Any advise is much appreciated.

 

[mikedt]

TubeMate is ad-supported and does pop-up ads. Pop-up ads are often for scareware(fake virus warnings), dating sites, offshore Viagra, cheap Rolexs, and other shady things. There's nothing truly malicious in it. Softonic of Barcelona are OK, they've been operating a software distribution portal since 1997. Don't know what AndroidFreeware is, their domain details are hidden behind an anonymous proxy. I'd guess it's Chinese or Russian.

It's not on Play, because Google dosn't allow software that violates their ToS, i.e. downloading videos from YouTube for off-line viewing.