Block "Unknown" Caller ID

[coope174]

I have been asked to block calls with "Unknown" as the caller ID. I know how to block calls from DID numbers. Can you block "Unknown" caller ID? I feel that if you can, it will block more than the call I want blocked. Potential client calls could be blocked as well.

12/1/2017 Update.
***The lack of replies tells me that I gave the correct answer to my manager. The answer is "No", you cannot block "UnKnown" caller ID. You can program vdn and vectors to handle calls without ANI but it would be a nightmare t program for individual phones at a large company.

[kumar1499]

if it is going via SBC, may be you can try to block such calls.

may be if vdn/vector tables allows you to use wild character, then you may need to add only number from 0-9 to validate the numbers