Finnish telcos co-operate to block spoofed caller id. The technology to do this has always existed - no receiving-side telco has to accept caller id signaling coming from wrong network, nor do the initiating-side telcos have to accept foreign ids in outgoing signals. Most telcos just don't care for their network integrity.
https://yle.fi/a/74-20052128?utm_source=social-media-share&utm_medium=mastodon

