Under what circumstances might it be ethical for the federal government to record or track calls or internet searches without any sort of warrant?

If the federal government has a strong and reasonable cause, then it may be ethical for them to track calls or internet searches without any search warrants. They can only do this if a person or group is clearly suspicious, and calls and internet searches can be used for a reasonable purpose. They cannot otherwise track calls or internet searches without a warrant, and it is illegal for them to track average people without reasonable suspicion.