Detecting Caller ID Spoofing Attacks (2013) [pdf]

I have a landline for my home alarm system and for having a common phone available for my family. I get approximately 15 telemarketing calls per day on it, all of which are using spoofed caller id and all of which are offering scam services like pretending to be a credit card company calling to lower the interest rate on my credit card.

The blocks work for about a week or two before they move onto new spoofed caller ID numbers, usually local phone numbers that match the area code and prefix of my own phone number. Now that I've run out of the 100 slots on my phone system to block various phone numbers, I'm considering just turning off the ringer.

Beyond systems using caller ID as a "password" of sorts, caller ID spoofing has made landlines all but useless due to marketing abuse.