How can I check for viruses on my iPhone?

Please explain what you mean by “attacking my WiFi”.

If you are having issues connecting to Wi-Fi, here are the troubleshooting steps recommended by Apple:

… If your iPhone or iPad won't connect to a Wi-Fi network - Apple Support

I would restart the Wi-Fi router and follow the other steps listed, would also remove any add-on VPN client apps, and would also test connecting with a different Wi-Fi network.

Failing that, contact Apple Support.

Malware causing this is unlikely.

only way to install any sort of software on a non jailbroken ios device is apples app store

so you can't get a virus (that is software) is if it came from apples app store where they have a lot of security

if It was me then I would read

If you think your Apple ID has been compromised - Apple Support

Here's the information you might find helpful:

"Installing software on a non-jailbroken iOS device is restricted to Apple's App Store, which provides a secure environment. Since apps on the App Store undergo strict vetting processes, the risk of downloading a virus is minimal. If you suspect your Apple ID has been compromised, consider reaching out to Apple Support for assistance."