When someone you don't know has your cell or home phone number, it can raise questions about your sense of security as well as privacy. The easiest way to deal with these and other "spoof" calls is to activate a block for unknown or unidentified numbers through your telephone service provider or in your cell phone's settings or tools options. For the most part, easy access for tracking withheld calls doesn't exist. But, there are a couple of ways to find out who's really calling if you have the time and the know-how.
Contact your local telephone service provider to set up a Call Trace feature with your service. By pressing "*57" immediately after disconnection, withheld calls will automatically be traced. This is a service for landlines only and usually only works in the local service area.
"Hack" your caller ID by forwarding your phone number to a VoIP number that is ultimately routed back to any phone with Caller ID capabilities. The number is first forwarded to a server that hosts Asterisk open source/free software, which is the same process used in private branch exchange (PBX) telephone systems. A specific script can be added to the Asterisk program to analyse incoming call information embedded in the blocking behaviour script used to hide numbers.
Set the Asterisk server to forward the call back to your phone. Once the information heading to your Caller ID is run through the Asterisk open source script, information on the origin of the call (as well as how it was hidden) is displayed on your phone's Caller ID in a readable format.
Type "Phone Tracing" in your Internet browser's search engine to locate online phone tracing services. Many of these services have access to a database that contains information on the ownership of numbers you don't recognise, including any "spoof" (fake) caller ID displays that are attached.If you have a VoIP system, you can automatically route anonymous calls to any number of tracing sites or through the Asterrisk software.
Blocking withheld calls is the easiest way to stop receiving them in the long run and is an option on most cell phones in the tools and set-up sections. Sometimes answering withheld calls and saying, "Operator, this is the caller," or "Trap," will make the caller think you are working with the police to collect evidence for prosecution and stop calling. This is especially effective with prank callers, or callers you feel are simply trying to annoy you. Most call tracing web sites and Reverse Call sites are owned and operated by the same generators of "spoof IDs," that can be purchased to make a call appear as a cell phone call or different state than the actual origination of the call(er.)
If you feel the number of withheld calls are become harassing or threatening - even an over abundance of hang-ups or heavy breathing, contact your service provider to work with local law enforcement agency to "trap" callers for prosecution. Be sure to confirm the methods and/or services you use are legal and provided by legitimate businesses.