Spam and annoying marketing calls have become a real scourge of modern digital communication. Every day, smartphone owners receive dozens of calls from debt collectors, unscrupulous sellers and scammers trying to steal confidential data. Calls when the screen displays “Unknown number” or “Hidden number” are especially annoying, since it is impossible to identify the caller until the answer is answered.
Fortunately, the operating system Android provides powerful built-in tools for filtering incoming traffic. In this article we will analyze in detail how to prevent calls from unknown numbers on Androidusing standard tools, third-party applications and special services of telecom operators. You will learn how to set up “white lists” and block anonymous calls in one click.
Using built-in Android blocking settings
The simplest and most reliable way to protect yourself is to use the functionality that is already integrated into your phone book. Most modern shells, such as MIUI, OneUI or clean Androidhave a section for managing the blacklist. To access these settings, open the Phone application and click on the three dots in the upper right corner.
In the menu that opens, select Settings, and then go to the Blocking numberssection. Here you will see a switch labeled “Block unknown/hidden numbers.” Activating this feature automatically rejects any calls where the caller ID is not reported to the network. This effective method is for those who expect calls only from saved contacts.
⚠️ Warning: Enabling this option may result in you miss an important call from a doctor, courier or government service if they call from a hidden number for technical reasons.
It is worth considering that the interface may vary slightly depending on the model of your device. For example, on smartphones Samsung the path may look like Settings → Number blocking → Block anonymous calls. On devices Xiaomi this feature is often hidden deeper in the call security settings.
Built-in blocking works at the system level and does not require the installation of additional applications, which saves battery power and RAM.
Setting up the "Do Not Disturb" mode for filtering
An alternative and more flexible solution is to use the Do Not Disturb (Do Not Disturb) mode. Unlike complete blocking, this mode allows you to set up exceptions, allowing calls only from selected groups of contacts, while all others, including unknown numbers, will be muted.
You can activate the mode through the quick settings panel by swiping from top to bottom, or through the menu Settings → Sound and vibration → Do not disturb. In the mode parameters, find the section Calls or Allow calls. Here you need to select the option “Only from contacts” or “Only from favorites”. All calls that do not meet these criteria will not sound.
- 📞 Only contacts: The phone will ring if the number is in your address book.
- ⭐ Favorites: only those you have added to the list of priority contacts will be able to call.
- 🔁 Re-call: a useful option that skips a call if the same number calls twice within 15 minutes (in case of emergency situation).
This approach allows you to maintain silence without creating a hard barrier for all unknown numbers, but only limiting their ability to disturb you with a sound signal. Calls may appear in the log, but the phone will not vibrate or ring.
Use of third-party anti-identifier applications
If the built-in tools are not enough, specialized applications such as Truecaller, Yandex.Who is calling or Kaspersky Who Callscome to the rescue. These apps use huge databases generated by the users themselves, which allows you to identify and block even those numbers that are not saved with you, but are marked by other people as spam.
After installing the application, you must grant it permissions to access calls and contacts. In the app settings, you should activate the function "Spam blocking" and “Blocking hidden numbers”. The algorithms of such services often work more accurately than standard Android tools, since they analyze the behavioral factors of the caller in real time.
⚠️ Attention: By providing access to contacts to a third-party application, you agree to the transfer of your phone book to the developer’s servers to replenish the common database. Read the privacy policy before installing.
Many of these applications have paid versions with advanced functionality, including complete silence for all numbers that are not in your contacts list. Free versions usually show the caller ID, but require your confirmation to drop the call.
How does the anti-identifier database work?
When a user marks a number as spam in the application, this number is instantly included in the cloud database. If another user with an installed application calls this number, the system automatically determines the category of the call (for example, “Collectors” or “Advertising”) and offers to block it.
Services of telecom operators to protect against anonymous calls
Mobile operators (“Big Four” in the Russian Federation and other providers) offer their own services to protect against unwanted calls. These solutions work at the network level, before the signal even reaches your smartphone. This is especially true if you are using a feature phone or an old Android model without advanced blocking functions.
The service can be called differently: “Caller Identifier” (paradoxically, this is often the name given to the service for blocking hidden incoming messages), “Black List” or “Spam Protection”. Connection is usually carried out through USSD commands, personal account or mobile application of the operator.
| Operator | Name of service | Cost (approximate) | Connection command |
|---|---|---|---|
| MTS | Black list | 1.5 rub./day | *111*442# |
| Beeline | Black list | 3 rub./day | *110*771# |
| MegaFon | Black list | 3 rub./day | *130# |
| Tele2 | Black list | 1.5 rub./day | *125# |
The advantage of network solutions is that they do not consume your phone’s battery and work even when the device is turned off (you simply won’t see a missed call from a blocked subscriber). However, to block precisely hidden numbers, you may need to activate the special option “Banonymous calls”, which not all operators have in the basic package.
Before activating a paid operator service, check your personal account - often the basic version of the "Black List" is included in your tariff plan for free or already activated by default.
Manual blocking via call log
Sometimes automatic filters miss annoying callers who change numbers or use ID substitution. In such cases, manual blocking through the call log is effective. This method requires user interaction, but gives you complete control over who can reach you.
Open the Phone app and go to the Recent or History tab. Find the number you want to block (even if it appears as “Unknown”, in some cases the system assigns a temporary ID to it). Press and hold your finger on the number or click on the i (information) icon next to it.
In the menu that opens, select the item Block or Add to blacklist. Confirm the action. After this, all communication attempts from that specific ID will be interrupted. On some devices, you can select the "Block and report spam" option, which will help improve the databases for all users.
- 📱 Quick access: Blocking is available directly from the missed call notification.
- 🗑️ Clearing the log: after blocking, it is recommended to delete the record of the call so as not to be confused in the future.
- 🔄 List management: do not forget to periodically check the blacklist and delete from there numbers that have become relevant (for example, the number of a new delivery).
Using forwarding codes and USSD
For advanced users, there is a blocking method through forwarding control codes. This method allows you to redirect all calls from unknown numbers to voicemail or to a non-existent number, effectively blocking them.
However, there is no universal code for all operators and phone models, since this feature depends on network support. The activation code for calling number identification is often used for outgoing calls, but for incoming calls the situation is more complicated. You can try entering the command:
**62*voicemail_number#This command redirects all calls when the phone is busy or unreachable. In combination with the Do Not Disturb mode, this creates the effect of complete isolation from unknown callers. To cancel the forwarding, use the code ##62#.
⚠️ Attention: Using USSD forwarding codes may result in charges for incoming calls while roaming or for voice mail services if they are not included in your tariff. Check the conditions with the operator.
There are also engineering codes for testing that can change the behavior of the radio module, but their use without in-depth knowledge can lead to network settings being reset. It is recommended to limit yourself to standard service management commands provided by the operator.
☑️ Checklist for complete anti-spam protection
Frequently asked questions (FAQ)
Will I see missed calls from blocked unknown numbers?
It depends on the blocking method. When using the built-in Android feature or apps, the call usually appears in the log as “Blocked” or simply disappears without a trace. When using operator services, the call may not be displayed at all, or an SMS notification of a communication attempt may be received.
Can I unblock a number if I accidentally added it to the black list?
Yes, it is easy to do. Go to your phone settings, section Blocking numbers or the blacklist application. There will be a list of all blocked contacts. Click on the cross or the “Unblock” button next to the desired number.
Will blocking unknown numbers help from scammers who pose as a bank?
Partially. Fraudsters often use number substitution (spoofing), masquerading as official bank numbers. Such calls will not be marked as “Unknown”, so the built-in anonymous blocking will not stop them. In this case, only anti-identifier applications with spam databases or attentiveness to the content of the conversation will help.
Does call blocking affect the speed of a smartphone?
Built-in blocking tools have virtually no effect on performance. Third-party applications may consume additional battery and RAM resources as they constantly analyze incoming traffic in the background. Choose lightweight applications with good reviews.
What to do if an important client calls from a hidden number?
In this case, it is better to disable complete blocking of anonymous numbers. Instead, use Do Not Disturb mode to allow calls from selected contacts, or ask the client to notify them about the call via instant messenger. You can also temporarily disable blocking during certain operating hours.