Some inividuals are concerned with the ethics of caller ID spoofing , this article is to help inform you of how it works. Caller ID and spoofing has been in the news lately and a big provider of calling cards for spoofing Caller ID systems, SpoofCard, was mentioned in a recent major motion picture, Untraceable. We have all heard about throw away cell phones and blocking our own Caller ID information for our outbound calls, but using a spurious phone number for our regular phones is a rather recent innovation made possible by technology. Caller ID is known as call Identification or CID, but should be known more properly as Calling Number Identification or CNID. It is a service offered by telephone companies that uses the information logged into your account and tied to your phone number (land line, VoIP, or cell phone). The caller’s phone number is transmitted to the recipient’s phone while ringing and if the name that matches the phone number is available and the recipient’s phone has the Caller ID service available the name will show up on the display as well. Spoofing Caller ID has long been used by private detectives and law enforcement in tracking down fugitives and to make sure that their sting operations are not exposed. Police will call a list of people that are wanted on warrants and told that they have won a prize and need to come to a particular location to pick it up. If the phone number on the caller ID read New York Police Department they would not get very many people caught up in their sting. You can choose to block your number on a per call or long term basis with some simple steps. Entering *67 before making a call will block the Caller ID form transmitting your information for that call only. If you want to block your ID for additional calls you will need to enter *67 for each call you make. If that becomes too difficult and you want to block the Caller ID information on all outbound calls you make you will have to make the choice with your phone service carrier. To unblock your Caller ID information for a particular call you will need to type *82 prior to dialing the desired number. With an all call Caller ID block in place you will need to type the *82 prior to each number called that you want to see your Caller ID information. Other options to reduce the chance of giving out your Caller ID information when making calls is to use the call screen feature that will block only a preset list of phone numbers from even ringing on your phone. There is usually a monthly fee for this service. You can block up to twelve numbers that can be changed at any time. This is especially helpful if you have been targeted by telemarketers or by someone harassing you after inadvertently giving out your caller ID info by not using a per line blocker of Spoofing system. Primary Rate Interface (PRI) lines are the lines that telephone companies provide to businesses that give a business or individual the capability of up to twenty three phone numbers per single PRI line. Enterprising individuals would buy some of these PRI lines and lease out some of the twenty three phone numbers to other private investigators for a charge. These professionals knew that Caller ID is not totally blockable and that calling 800 numbers would allow their information to be viewed so that using these so called “blind” numbers would assure their identity would remain hidden. There were several services that offered these blind numbers discreetly within the security and investigation industries. These phone hackers continued to refine their techniques and as computer language became more complex and integrated in the use of phone systems, when VoiceXML became popular in phone systems that are not hard wired and run through servers, they found that the VXML could be made to imitate the PBX functions of hard wired systems and set your Caller ID to whatever you wanted it to read. Then when VoIP became a popular alternative to land lines, hackers found a loop hole in the Vonage sign up system that allowed you to give any number as your Caller ID when you ported your existing number to Vonage. Other open source PBX programs have allowed hackers to create applications that would enable users to easily spoof their Caller ID for any situation. The same day a company called Telespoof launched a service to compete with Star38 and offered their service through an 800 number. Shortly after that another company called Covert Call would offer Caller ID spoofing through both a web base and an 800 number. Both Covert Call and Camophone websites had very little information or marketing glitz to set them apart and once their systems were hacked and their user information was published on the internet they shut down in 2005. SpoofCard became the first service to offer recorded calls, and the ability to change your voice, even from male to female and the reverse as well, along with offering service via the web or via an 800 number. As calling cards go the minutes you purchase from SpoofCard are not that bad at about six cents per minute. You can use it as a regular calling card or add the spoofed Caller ID as you wish. Other companies like Telespoof.com and Phonegangster.com offer similar calling cards for a little less and all offer a free trial call so you can check out their services.

Caller ID spoofing is fooling the computer network the runs the telephone system to show a number on the receivers caller ID display which isn't the number actually associated with the originating line.  Caller ID spoofing can make a call appear to have come from any phone number the caller wishes. People have often misplaced trust in the caller id system and spoofing can call the system's value into question.

From How Stuff Works: "If you have a Caller ID box attached to your phone, then an amazing thing happens every time your phone rings -- the number (and sometimes even the name) of the calling party appears on the display right after the first ring! It turns out that the process of making the caller ID display possible is remarkably simple at your end of the line. If you have read the HSW article entitled How Modems Work, then you know that the early modems used a technique called Frequency Shift Keying to transmit bits over a phone line. FSK is extremely simple: One tone (or frequency, like 1,200 Hertz) represents a binary 1, while another tone (like 2,200 Hertz) represents a binary zero. A modem changes frequencies depending on whether it wants to send a 1 or a 0. How quickly it changes frequencies determines the speed, or baud rate, of the modem. To send caller ID information you your home, the phone company uses an FSK technique identical to a 1,200 baud modem and it sends ASCII character data to the caller ID box. The modem message is sent between the first and second ring (see How Telephones Work for a description of how the ring signal works). So the phone rings once, and if you could listen to the phone line just after that ring, you would hear a "bleeeep" sound about half a second long. If you decoded the bleep, you would find that it contains (in the simpler of the caller ID systems):

• A series of alternating 1s and 0s to help the caller ID box get the timing down
• A series of 180 1s
• A byte representing the type of message
• A byte representing the length of the message
• Month, day, hour and minute, each represented with a pair of bytes
• The 10 digit phone number in 10 bytes
• A checksum byte

There is also a more advanced system that contains the caller's name, etc., but its technique is identical (see the second link below for details). Each character is sent as a standard 8-bit ASCII character preceded by a "0" start bit and followed by a "1" stop bit. The caller ID box contains a modem to decode the bits, a little circuit to detect a ring signal, and a simple processor to drive the display. That's really all there is to the whole thing! For more information and links to related articles, see the next page. "

There are many ways to faking your caller ID.