How to block SMS without a number on Xiaomi Redmi: the full guide

The problem of intrusive messages from unknown senders is familiar to every smartphone owner. This issue is especially acute for users of the Xiaomi and Redmi ecosystem, where aggressive advertising policies of some services and spam mailings can turn receiving notifications into torture. Often there is a situation when you need to completely close the communication channel with a particular source without storing its data in the device’s memory.

In Android, as well as in the proprietary shell of MIUI or its successor HyperOS, filtering mechanisms work at the system application level. This means that blocking occurs before the message is displayed to the user. However, standard methods often require contact creation, which is not always convenient. In this article, we will discuss professional methods to isolate an unwanted sender using hidden system capabilities and specialized filters.

Effectiveness of spam control depends on a proper understanding of how the Android handles incoming data packets. It's important not just to delete the message, but to set up preventive protection. We'll take a look at the technical details of blacklists and show you how to get your phone to ignore signals from certain sources, even if their number is not saved in your notebook.

The principles of filtering messages in MIUI and HyperOS

Xiaomi's security system is built on layered security, which involves analyzing a database of spam numbers and user complaints. When you receive a message, it first passes through the Security application filter. If the number is not in the global databases, the system checks the local settings of the device, and this is where you can lock without saving contact.

The key element is the Blacklist, which functions independently of the phone book, which allows you to enter any number sequences or even keywords into it. When a message arrives, the system checks the sender's data against that list, and if a match is found, the message is quarantined or deleted instantly without creating an audible alert.

It is worth noting that MIUI algorithms allow you to block not only specific numbers, but also entire ranges or types of messages, for example, you can configure a filter to block all messages containing certain words, which is especially effective against advertising mailings from delivery services or bank shares coming from short numbers.

⚠️ Warning: When manually configuring filters for keywords, be extremely careful. Blocking overly generic words (e.g., code, promotion, bank) can result in the loss of important notifications from real services.

Blocking through the built-in "Security" application

The most reliable way to avoid installing third-party software is to use the regular Security app, which is pre-installed on all Redmi and Poco devices and has deep access rights to the system, and to get started, you need to run the application and find the partition responsible for blocking.

The interface may vary depending on the firmware version, but the logic remains the same: you need to go to the locker settings menu, you can activate the Blacklist mode and add a number manually, and the main advantage of this method is the ability to add a number that is not in the contacts, just by entering it with numbers.

The algorithm of actions is as follows:

• 📱 Open the Security app (Icon with lightning or shield).
• 🚫 Select the Block or Antispam option.
• ⚙️ Click on the gear icon (Settings) in the upper right corner.
• ➕ Select the Blacklist and add the number you want manually.

Once you add a number, all incoming calls and messages will automatically be rejected, the system will not show pop-up notifications, and the fact of blocking can be checked in the event log of the application, which creates the illusion that messages from this sender simply do not come, which is required in most cases.

Use of hidden codes and engineering menu

For advanced users who want to gain maximum control, there are hidden features of the system. MIUI Access to advanced locker settings through special USSD-It's a code or an engineering menu, and it allows you to manage the lock list at a deeper level.

One way is to directly enter a command into the dialer (the Phone app), and although there is no universal code for all models, often a sequence opens the call and message lock settings. Try entering the ##4636### code to log into the test menu, but SMS is often accessed through the messaging app settings.

A safer method is to use the command line via ADB (Android Debug Bridge) if the phone is debugging over USB, which allows you to add numbers to the system blacklist without going through the GUI.

adb shell settings put secure blacklist_numbers"+79990000000"

Using ADB requires a computer connection and appropriate drivers, and the good thing about this method is that it can script the process and add hundreds of numbers from a text file at once, which cannot be done manually through the phone interface in a reasonable time.

⚠️ Note: Making changes through the engineering menu or ADB-The commands can cause the system to run in an unstable way if you're not sure what you're doing. Always back up the data before the experiment.

Blocking for Keywords and Content

Often spammers change sender numbers, but the content of messages remains template, in such cases, text filtering works better, Xiaomi's built-in tools allow you to create rules that block messages containing certain phrases.

To configure this functionality, go to the blocker settings and look for "Keyword Filter" or "Block by Text." Here you can add words specific to spam: "win", "credit", "card", "promotion". The system will analyze the body of each incoming message and block those that contain prohibited tokens.

This method is ideal for dealing with mailings from bookmakers and chain stores, but it requires periodic word list updates, as spammers are constantly coming up with new workarounds using special characters or replacing letters (for example, "credit" instead of "credit").

Example of effective keywords to block:

• 💸 Bet, winning, casino, slots.
• 🏦 Credit, loan, card, approval.
• 🎁 Gift, bonus, promotion, sale.

Third-party applications for advanced filtering

If built-in tools are not enough, specialized applications from Google Play come to the rescue, with SMS Blocker, Truecaller and Should I Answer leading the niche, using cloud-based databases updated in real time by millions of users.

The main advantage of third-party solutions is the ability to block messages from numbers that are not in your book based on the number’s global reputation, and the app automatically detects that the number belongs to the spammer and blocks it even before it appears in the notification list.

But installing these applications requires broad permissions, and it has access to read all your SMS and call history, and it's necessary for the filter to work, but from a privacy perspective, it's a trade-off, and you only have proven open source or reputable solutions.

💡

For maximum efficiency, combine methods: use a built-in blacklist for known enemies and a third-party cloud-based app to protect against new spam.

Journal analysis and exception management

Once you set up the lock, it is important to check the log of blocked events regularly, and the Security app has a tab called "Journal" or "History" that displays all communication attempts that have been interrupted by the system, which makes sure that the lock is working correctly and that you have not lost anything important.

Sometimes legitimate messages, such as bank confirmation codes, can be blocked if they contain a stop word, in which case you need to add the sender to the Whitelist, and messages from the whitelist numbers are filtered and always delivered to the user, ignoring any prohibitions.

Regular blacklist cleaning is also necessary. Numbers can be resold, and yesterday's spam number can be used by an ordinary person today. Delete old records so as not to block potentially useful contacts.

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Regularly checking the lock log is the only way to ensure that the system is working correctly and does not miss critical notifications.

Frequently Asked Questions (FAQ)