iOS update? Hope it was Apple

Scams. Emails stating you have malware are always scams. An iPhone cannot get malware. See here: link-> Recognize and avoid phishing messages, phony support calls, and other scams - Apple Support

You can always go to Settings->General->Software Update at any time to verify if there are any updates available you can download.

That would have been a scam message. Apple would not send a message regarding possible malware.

Depending on the source of the email it could be true or false.

There is no malware that can affect an iPhone. There is no way for you to download any malware to an iPhone.

And again such emails are always false. It will never be true on an iPhone.