as I was playing a game on my iphone6, a message popped up with a warning. It come through Safari and read more or less: 'the last website you visited has corrupted your phone with a Trojan; would you like to upload an update'. Message was supposedly from Apple, but the site address it came from, had nothing to do with Apple: sgjh.com or something like that. Two options given: upload or delete. I simply switched that page off. I'm worried: is there a way to make sure there is no virus on my iPhone? Any app/software?