Malicious (robo)callers often alter the calling number of their outbound telephone calls in order to deceive the called party and have the called answered. There is a wide range of deceptions derived from changing the CLI, from making the call to appear like a neighbor is calling, to impersonating an official agent (policy, IRS). The STIR & SHAKEN implementation in OpenSIPS is a way to fight back such deceptions by ensuring that the calling number of a telephone call is secure and fully trusted.