How do I detect and remove virus on my iPhone?

Helpcpt (Author)

More likely, your device has encountered a notification or false claim

initiated by some syndicate or group, in an attempt to gain information

from any response they could use as an exploit, to leverage access.

Recognize and avoid social engineering schemes including phishing

messages, phony support calls, and other scams - Apple Support

//support.apple.com/en-us/102568

These various types of subterfuge or fake urgent lies are attempts to

get you to reveal your personal Apple Account information; don't do it.

More concise advice and instructions per Apple Support links, here:

Get help with security issues - Apple Support

//support.apple.com/en-us/111756

Helpcpt wrote:

I was browsing on the web and I got a notice saying my phone has a virus.

Sounds like you saw lies from criminals, who were trying to fool you into

• Contacting them for "help" ("help" in emptying your bank account or running up charges on your credit card)
• Purchasing a worthless "security" app that would do nothing to solve the made-up "problem".

Don't fall for the scam!

U.S. Federal Trade Commission – How To Spot, Avoid, and Report Tech Support Scams

What is clear is that those messages are scams and your phone does not have a virus. We do not know if you called a number or downloaded any software that was recommended in that message. You also have not described what you mean by your phone "acting weird".

Those types of messages are more common when browsing less than legitimate websites. They were paid to present that pop up to you.

All pop ups telling you that you “have a virus” are scams.

ALL of them.

If your iPhone has been updated to the latest version of iOS, it is extremely unlikely your phone has been infected by a virus. If you could describe details of how it is "acting weird," someone may be able to tell you more about what is happening.