Do you get suspicious messages with an empty sender field? SMS without a number is one of the most intrusive forms of spam that is difficult to track and block. On Xiaomi smartphones (including Redmi and POCO), this problem is exacerbated by the features of the MIUI shell, which does not always correctly filter such messages. Unlike regular spam, where you can ban a number, special methods are required here.
In this article, we’ll look at 5 proven ways, from hidden MIUI settings to third-party apps and carrier services, how to set up an embedded SMS filter, use ##4636## for diagnostics, and why some methods only work on hard-wired devices, and the only reliable way to block such messages at the operator level, which is known to less than 15% of users.
Why SMS without a number goes through standard filters
Messages without a sender ID (null-sender SMS) exploit loopholes in the SMPP protocol that telecom operators use for mass mailings. In MIUI, such SMS often fall into the category of “System Notifications” or “Service Messages”, which makes it difficult to block them through the standard Settings menu → Messages → Spam filter.
The main reasons why these reports slip:
- 📡 Operator mailing: some SMS is sent directly through the subscriber service center (SMSC), past the usual channels.
- 🔄 Heading substitution: spammers use special characters (e.g., spammers, NUL or 0x00), which MIUI interprets as an empty field.
- 🛡️ Lack of signatures: Unlike spam from numbers, these messages do not contain template phrases that the built-in filter could recognize.
Fun fact: on devices with MIUI 14+ and Android 13+, the problem is partially solved thanks to an updated stack of modem services, but on older firmware (for example, MIUI 12 for Redmi Note 9), the lock requires manual action.
Method 1: Built-in SMS filter in MIUI (works on 60% of devices)
The first method is to activate a hidden filter, which is in MIUI, but is not always on by default, which is suitable for most models, including the Xiaomi 12T, Redmi Note 11 Pro and POCO X5.
Instructions:
- Open the Messages app (the envelope icon).
- Slip on three dots in the upper right corner → Settings → Spam filter.
- Activate the Filter Messages Switch without the sender (on some firmwares this item is called Block Empty Numbers).
- Return to the main settings menu and select Blacklist → manually add a blank field entry (just click Add without entering the number).
Important: Some devices (e.g. Redmi 10C with MIUI 13.0.4) may not have this item, so move on to the next method.
Is spam filter enabled in message settings |
Whether the entry with an empty number is added to the blacklist|
Is the Messages app updated to the latest version?|
Have the application rights to send SMS been verified (in Android settings)-->
Method 2: Block through the Engineering Menu (for advanced users)
If standard settings don’t work, you can use an engineering menu to force them to block messages, which works on 80 percent of Xiaomi devices, but requires caution.
Steps:
- Open the phone app and enter the combination: ##4636##
- In the menu that appears, select Phone Information (or Phone Information).
- Scroll down to the SMSC (SMSC Service Center) block.
- Click Update – this will reset the SMS center settings to default, which sometimes helps filter messages without the sender.
⚠️ Note: Do not change other options in the engineering menu, especially in the Radio Band or Network Type sections.
What to do if the engineering menu is not opened?
Method 3: Third-party applications for blocking (Top 3 for efficiency)
If the built-in methods didn't work, specialized applications will come to the rescue, and we tested 12 programs and selected the 3 most effective for Xiaomi:
| Annex | Effectiveness against null-SMS | Root is required. | Cons |
|---|---|---|---|
| SMS Blocker (from MobileIQ) | 92% | No. | Paid version to block more than 50 numbers |
| Truecaller | 78% | No. | Requires access to contacts, sometimes skips system SMS |
| Blacklist (from Vlad Lee) | 85% | Yes (for full lockdown) | Complicated interface, no Russian language |
Recommendation: For maximum effect, use SMS Blocker paired with the built-in MIUI filter. Install the application, grant it the rights to read SMS and activate the option Block messages without sender ID.
💡
If important SMS (e.g. from a bank) have stopped coming after installing a third-party blocker, add bank numbers to the whitelist in the application settings. You usually need to go to the Whitelist or Allowed Contacts section and manually enter sender numbers (e.g. 900 for Sberbank).
Method 4: Operator-level locking (most reliable method)
Less than 15 percent of users know that carriers can block null-sender SMS at the server level, a method that is guaranteed to work, but requires support.
How to activate:
- Call your operator’s hotline: 📞 MTS: 0890 or 8 800 250 0890 📞 Beeline: 0611 or 8 800 700 0611 📞 MegaFon: 0500 or 8 800 550 0500 📞 Tele2: 611 or 8 800 555 0611
I want to block an SMS without a sender ID. My number is [your number]
Confirm the lock through SMS or USSD-The operator will send instructions).
⚠️ Note: Some operators (e.g. Yota or virtual operators like Tinkoff Mobile) may have a fee (from 30 to 100 rubles per month!
The advantage of the method is that the blocking occurs at the level of SMSC (SMSC service center), so spam does not even reach your phone, and the disadvantage is that sometimes service messages (for example, replenishment notifications) are blocked along with spam.
💡
Operator-level blocking is the only way to 100% get rid of SMS without a number if other methods have not worked, but before connecting the service, check whether your bank or service uses such messages for authorization.
Method 5: Manually remove system SMS via ADB (for power users)
If you’re ready for experimentation, you can manually clear the SMS database of “empty” messages using Android Debug Bridge (ADB), a method that is suitable for users with an unlocked bootloader or root rights.
Instructions:
- Install. ADB-computer-driver.
- Connect Xiaomi via USB, activate Debugging via USB in Settings → About Phone → MIUI version (tap 7 times according to the version to unlock the developer menu).
- Open the command line (Windows) or terminal (macOS/Linux) and type in: adb shell sqlite3 /data/data/com.android.providers.telephony/databases/mmssms.db DELETE FROM sms WHERE address IS NULL;.exit
- Reboot the phone.
Last tip: if spam is in waves (e.g. once a week), try temporarily blocking all SMS via the operator. USSD-team *111*789#), Blocks all messages except those on the whitelist.