*67 - Selective Call Display and Wardialing
*67 prevents the display of your name and number on a per-call basis. You do not have to order this service as it is already on your phone line and you can access it free of charge. If you wish to block your name and number from being displayed press *67 before you place your call (1167 for rotary phones). A message will inform you that "Call Block has been enabled, wait for dialtone and finish dialing". The words "unknown name/private number" will be displayed instead of your name and number. You must do this every time you want to block your name and number.
*57 - Call Trace
*57 defeats *67. However, it is a hassle, it costs $3.00/use, and unless you are being particularly harassing most people won't bother. The information from traced calls is sent to telco security who, on request, provides the information to the police. Call Trace information is not released to customers. Use 1157 for rotary phones.
*67 is useful for war dialing. It provides a thin layer of anonymity which eliminates annoying callbacks. Another option is to forward all incoming calls to a number that does not answer.
The only draw back to this method is time. It takes a significant amount of time to dial the extra digits, wait for the message, wait for dialtone, and dial the number. Telus makes the problem worse by randomly altering the delays between when the *67 is responded to and between the end of the message and the dialtone. The whole process can take up to seven seconds before you get dialtone. This requires a delay in your dial string. I usually use a dial string format of *67,,,,,,,###-#### to create a sufficient delay. (That's 7 commas, 1 comma=1 second delay.) Make your prefix *67,,,,,,, and set your communications software to use the prefix when dialing. Test it and determine how short you can make the delay. (Note: 1167,,,,,,, works great too. 11 is the same as *.)
I have only been called once by telco security when somebody bitched that I (my modem) phoned them and hung up ("hello?" <ALT-H>) at 3:00 AM or something. Go figure. I said I just got my modem and was trying some numbers from a BBS list, I'm really sorry if I disturbed somebody. She said no problem, she just has to check.