Rosh Hashana 2:1

If a witness is unknown, another person accompanies him to testify about him. Originally, testimony about the new moon was accepted from anyone. When heretics started interfering, it was instituted that testimony could only be accepted from known witnesses.

Rosh Hashana 2:2

Originally, bonfires were lit on mountaintops to notify the people about the new moon. When the Samaritans started interfering, it was instituted that messengers should be sent instead.