Why is my iPhone 6s suddenly so slow?

Your iPhone is too old and has reached its end-of-service.

Good News:

You are eligible for an upgrade‼️

Click ▶︎ Apple Trade-In.

But wait, it gets better:

Here’s more:

See you soon at your local Apple retail store‼️

If you didn't jailbreak it, you don't have a virus.

Chances are the battery is on its last legs and can no longer supply sufficient power to run the processor at full speed.