How to identify and remove Trojan Viruses on iPhone?

… Facebook …

You know where the problem comes from, yet you continue to go there. You may want to change that.

… says APPLE SECURITY and it said that my iPhone has been infected by A TROJAN VIRUS

All nonsense, no web page can determine that. It’s an ad. The advertised app is the Trojan, in that it presents itself as something it is not.

and it advised me to install an App called “ InvisiGuard VPN “

That is the product being advertised. It doesn’t protect you from viruses, it probably doesn’t help you with anything you do. 99.9% of the users do not need a VPN on their phone. And if you do need a VPN, then don’t choose one with this aggressive advertising.

I install it but suddenly realise that this may not be from APPLE itself … I have left it on for about 2 minutes as I was trying to contact my IT friend to check with him. He advised me to quickly uninstall the app . I deleted and uninstall it ..

Installing alone doesn’t do anything. It can only do things if you open the app and use it.

Check Settings﹥VPN and Device Management﹥ to see if the app left any traces there.

Please advise whether I am in any kind of DANGER with regard to my iPhone contacts , information and passwords which are all stored on my iPhone

All (third party) apps on iPhone are “sandboxed” so that they can’t access anything that you haven’t given permission for. You and your data are fine.

You were not directed to Apple Support or Security.

The message that you received was a scam that is trying to trick you into buying useless software that will do nothing to help your phone. But it will slow it down and put money in the pockets of the scammers selling this junk.

You did the right thing by deleting the VPN. No worries.

Watch out for more scams. They are everywhere.

The page that popped up was a scam, full of lies. It was a good idea to delete that app.