Do Star Codes Like *77 or #662# Block Spam Calls?

Star codes like *77 and *662 provide basic carrier-switch call filtering, but they cannot stop modern robocallers who spoof real 10-digit phone numbers. While these vertical service codes were useful in the landline era, contemporary spam operations easily bypass them using automated VoIP platforms.

What Do Common Telecom Star Codes Actually Do?

Vertical service codes (star codes) are legacy telephony commands sent directly to your telephone carrier's local exchange switch. Here is what the most common blocking codes do:

• *77 (Anonymous Call Rejection): Instructs the central office switch to reject incoming calls where the caller ID is explicitly marked as "Private," "Blocked," or "Anonymous." Callers receive a recorded intercept asking them to unblock their number.
• *87 (Disable Anonymous Call Rejection): Deactivates *77 call rejection on the line.
• *60 (Call Block / Selective Call Acceptance): Allows users on supported landlines to create a static list of up to 12 specific numbers to reject.
• *662# (T-Mobile Scam Block): A modern mobile network feature code that activates T-Mobile's network-level Scam Likely filter directly on the carrier core.

Why Do Star Codes Fail Against Modern Caller ID Spoofing?

The fundamental limitation of star codes like *77 is that robocallers almost never place calls with private or anonymous caller ID tags. Scammers know that anonymous calls have low answer rates. Instead, they use SIP trunking and VoIP software to forge legitimate-looking 10-digit phone numbers that match your local area code.

Because the incoming call presents a valid 10-digit number, carrier switches evaluating *77 rules allow the call to pass through immediately. Similarly, static blocking codes like *60 are useless against scammers who generate thousands of new numbers daily.

How Does Modern On-Device Call Screening Replace Star Codes?

Rather than relying on primitive switch rules, modern smartphones utilize deep system-level APIs such as the Android ROLE_CALL_SCREENING API. This subsystem allows specialized security software to inspect every incoming call before the ringer sounds.

Instead of merely checking whether a number is hidden, on-device screening inspects the carrier's STIR/SHAKEN cryptographic signature, checks the number structure against high-risk pattern databases, and evaluates frequency behaviors. To learn more about this architecture, explore how 26-layer on-device call screening works.

What Is the Most Effective Way to Stop Unsolicited Calls?

While enabling carrier features like *662# provides a helpful baseline, complete protection requires proactive, on-device intelligence. On-device screening evaluates calls in milliseconds, ensuring that contacts, call logs, and audio never leave the device. Review the full suite of Callro on-device screening features to see how hardware-level inspection stops unwanted calls before your phone rings.