After just a few days, I am starting to see more unverified and, presumably, spoofed CID numbers. How to deal with these, apart from not answering, is the same old problem.
I took a look at some of the "spam blockers"; one of them says this:
Spam blocker will categorize and label nuisance calls into three categories based on level of risk. “High Risk” calls will be blocked, “Medium Risk” calls will be sent to voicemail, and “Low Risk” calls will ring through to your phone and show as “Spam?” on your Caller ID. You will have the ability to adjust these settings to meet your needs.
Given that there is no point in blocking a spoofed caller ID, it seems (I have a sneaky suspicion) like blocking based on adjustable rules is an unnecessary and ineffective approach. The whole STIR/SHAKEN protocol is to use a certificate based system to authenticate caller ID - no? This "spam blocking" approach appears to be ill-advised unless it is a tacit admission that the protocol is already a fail.