How to permanently lock an unknown number on Xiaomi Redmi: from standard settings to secret chips

Calls from unknown numbers, intrusive spam from banks or fraudulent SMS are a problem that every Xiaomi Redmi owner faces. Even if you don't pick up the phone, constant notifications are annoying, distracting and eating up battery power. Fortunately, MIUI offers several built-in tools to block unwanted contacts, and third-party apps extend the capabilities to the level of "anti-spam shield".

But there's a nuance here: not all methods work equally well, like Redmi's standard Blacklist, which might not block numbers with spoofed identifiers (so-called spoofing calls), and some Google Play apps require root rights to work properly. In this article, we'll look at 5 proven ways, from basic to advanced, that will help get rid of intrusive subscribers forever.

Special attention will be paid to the hidden MIUI Keyword Block feature, which allows you to automatically send spam SMS with certain phrases (for example, “you won prizes” or “pay the penalty urgently”), this tool is only available on MIUI 13+ firmware and often goes unnoticed by users.

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1. Standard blacklist in MIUI: how to add a number manually

The easiest way to block an unknown number on Xiaomi Redmi is to use the built-in Blacklist, which works on all models (from Redmi 9A to Redmi Note 12 Pro+) and does not require additional applications to be installed, but it has a limitation: the lock only works for saved or recent contacts, if the number is hidden or changed, this method may not work.

To add a subscriber to the blacklist:

• 📱 Open the Phone app (the tube icon on the home screen).
• ⚙️ Click on the three dots in the upper right corner and select Settings → Blacklist.
• ➕ Tape the + icon at the bottom of the screen.
• 🔍 Select a number from the Call Log or enter it manually in the Add manually field.
• 🔒 Confirm the addition by clicking Ready.

After that, all calls and SMS from the blocked number will be automatically ignored. Notifications of missed calls will not appear, but information about them will be stored in the → Spam Journal.

⚠️ Warning: In some regions (e.g. Russia), mobile operators may use number swapping technology (CLIP), which causes spam calls to appear as "Unknown" or "Hidden". In this case, the standard Redmi blacklist is useless - alternative methods will be required (see Section 3).

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2. Automatically block spam via MIUI settings

MIUI 12 and later has a built-in spam protection mechanism that analyzes incoming calls and SMS from Xiaomi’s database, a feature called Spam Protection and is based on machine learning, which automatically detects fraudulent numbers and prompts them to block.

To activate the protection:

1. Go to Settings → Applications → Phone → Spam Protection.
2. Turn on the spam filter switch.
3. Activate options: 📞 Block spam calls 💬 Block spam -SMS 🔔 Show blocking notifications (optional)

Sources of spam

Xiaomi Cloud Database

Local data

Once activated, the system will begin to analyze incoming calls, and suspicious numbers will be marked with a red exclamation point in the Call Log, and you can block them in one tap by clicking on the 🚫 icon next to the number.

⚠️ Attention: If you use Redmi with global firmware (e.g., MIUI Global), the cloud spam database may not work in Russia and CIS countries due to Xiaomi's restrictions on processing personal data. In this case, it is recommended to additionally install the application from your mobile operator (e.g., "MTS Protection" or "Beeline Blacklist").

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3. Blocking hidden and unknown numbers: workarounds

One of the most unpleasant types of spam is from hidden numbers (shown as "Unknown", "Private Number" or "Anonymous"). Standard MIUI tools can't block such calls, but there are a few workarounds:

Method 1: Use the USSD code

Some operators support the blocking of hidden numbers through the USSD- command, for example, for MTS and Beeline, the command is suitable:

*111*301#

After dialing and calling you will receive an SMS with instructions for activating the service. The service is paid (about 3-5 rubles per month), but reliably filters all incoming calls without an ID.

Method 2: Blocking applications

Apps like Truecaller or CallApp can block hidden numbers, but require additional permissions:

• 🔓 Permission to Read Call Log
• 📱 Permission to Change System Settings (for some functions)
• 🔄 AutoRun permission (to keep the application running in the background)

We recommend Truecaller – it has the largest database of spam numbers (more than 300 million records) and is able to recognize fraudulent schemes by keywords in SMS. However, please note that the application collects data about your contacts (this is spelled out in the privacy policy).

Method 3: Operator setting

Most Russian operators have free services to block spam:

• 📡 MTS: Service "Spam Protection" (activated via personal account or USSD *111*254#).
• 📡 Beeline: "Antispam" (included in the "My Beeline" appendix).
• 📡 MegaFon: "Protection against fraudsters" (available in the "Services" section of the personal account).
• 📡 Tele2: Stop Spam (free for all fares).

⚠️ Warning: If you use Redmi with two SIM- cards, the spam lock settings will have to configure separately for each operator. In some cases, the operator's services may conflict with the built-in filter MIUI, so check the call log for missed important calls after activation.

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4. Keyword blocking in SMS (hidden MIUI 13+ function)

Few people know, but MIUI 13 and later has a hidden feature that allows you to block SMS not only by numbers, but also by keywords, for example, you can set up automatic deletion of messages with the words "you won", "pay urgently" or "your account is blocked", a feature that is especially useful for combating phishing.

To activate it:

1. Open the Messages app.
2. Slip on three dots in the upper right corner → Settings → Spam filter.
3. Turn on the Keyword Filter switch.
4. Click Add Keyword and enter phrases that should be blocked (e.g., “gift card”, “traffic police fine”, “loan online”).
5. Select the action: Delete the message or Move to spam.

It works in the background and does not require an internet connection, but it does not block calls, only SMS. It is also worth considering that too general keywords (such as "bank" or "payment") can lead to false positives.

Important: this feature is only available on MIUI 13 firmware and later. Redmi with MIUI 12 or custom firmware (for example, LineageOS) does not.

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5. Advanced methods: ADB and root access

If you're willing to take drastic measures, you can lock up unknown numbers at the system level, and these techniques require technical skills and can lead to a loss of warranty, but they give you 100% success.

Method 1: Blocking through ADB

With Android Debug Bridge (ADB), you can disable incoming calls from hidden numbers.

1. Activate Developer Mode on Redmi (go to Settings → About Phone → MIUI version and tap 7 times on the build number).
2. Enable USB debugging in Settings → Additional → For developers.
3. Connect your phone to your PC and execute the command: adb shell settings put global block_unknown_callers 1
4. Reset the device.

All calls from unknown numbers will be automatically reset. To cancel the lock, use the command:

adb shell settings put global block_unknown_callers 0

Method 2: Editing a build.prop file (requires root)

If you have root access, you can manually add lock rules to the system file:

1. Install a file manager with root support (such as Root Explorer).
2. Open /system/build.prop file in the text editor.
3. Add the line: ro.telephony.call_blocking_enabled=true
4. Save the changes and restart the phone.

⚠️ Warning: Incorrect editing of the build.prop file can lead to bootloop. Before making changes, back up the file. Also note that after the MIUI update, all edits to build.prop will reset.

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If you don’t want root access but need an extended lock, try F-Secure’s Call Blocker app, which doesn’t require root, but has a paid subscription (about 300 rubles a year) and runs through a cloud base.

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6.What to do if the lock is not working?

Sometimes even after you add a number to the blacklist, the calls keep coming in, and here are the possible reasons and solutions.

If none of the methods worked, try resetting the phone app settings:

1. Go to Settings → Applications → Application Management.
2. Find the Phone app and select Warehouse.
3. Click Clear Data and Reset Settings.
4. Restart the phone and set up the lock again.

Alternative calling apps such as Google Phone (which has a built-in spam filter) or Drupe (which supports blocking by regular expressions) can be considered as a last resort, however, they can conflict with Xiaomi’s native app.

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7. How to unlock the number if you change your mind?

If you accidentally add a number to the blacklist or need to temporarily unlock the contact (for example, for an important call), you can do this in a few seconds:

Through the phone settings:

1. Open the phone → Blacklist.
2. Find the number in the list and swipe it to the left (or click on the three dots next to the number).
3. Select Remove from the blacklist.

Through the call log:

1. Open the Call Log and find the number that is blocked (it will be marked with a red icon 🚫).
2. Slip the number and select Unblock.

If the number has been locked through Truecaller or another third-party application, unlocking must be done in the settings of this application.

⚠️ Warning: Once the number is unlocked, all missed calls and SMS will not be recovered. If you need to keep your correspondence history, back up your messages before blocking (e.g., via SMS Backup & Restore).

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FAQ: Frequent questions about room locks on Xiaomi Redmi