Call masking works within a company's VoIP phone system to set the outbound phone number for each phone call. Since masking services can be abused, reputable cloud phone systems require proof of ownership before changing the outbound caller ID. As calls are placed into the telephone network, header information for the call is provided. Generally, the telephone network "trusts" any caller ID that is provided, thus it's ripe for abuse. Technological advancements have now made it possible to authenticate calls — a technique known as STIR/SHAKEN.