How to block text messages from unknown numbers

If your phone is overrun with spam text messages from random unknown senders, it’s understandable that you’re looking for solutions. Not only does it make finding messages you actually want to read difficult, but you also suffer constant disruptions throughout the day. What’s more, a significant proportion of spam messages can actually be dangerous, containing phishing attempts, scams, and links to malware. 

Stopping spam on your phone can be tricky. But we’ll help you block messages from unknown numbers—whether you have an iPhone or Android device, use only your default messaging app or prefer other apps like Viber.

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1) Block specific numbers

The first step you can take to reduce the number of spam text messages you receive is to block specific phone numbers. Spammers usually have a list full of numbers they periodically contact so blocking the unknown numbers you have cluttering your messaging apps right now will prevent the same numbers from bothering you in the future. 

Here’s how:


  1. Open your messages app
  2. Find and tap on the sender you want to block. 
  3. Tap the three dots in the top-right corner to open the menu. 
  4. Make sure the “report spam” box is ticked and click “ok.”


  1. Open your messages app. 
  2. Find and tap on the sender you want to block.
  3. Tap the number or the name at the top.
  4. Tap “info.”
  5. Tap “block this caller.”

2) Filter unknown senders and spam text messages using your device

The next thing you should do is filter out spam. It’s not a perfect solution, as some text messages from unknown senders may still make it through, but if you’ve already blocked the repeat offenders (the unknown numbers you blocked in Step 1), this should do a decent job cleaning up the rest. 


  1. Open your phone app
  2. Tap “more” and go to “settings.”
  3. Tap “blocked numbers” and turn on “unknown.”

If you’re using the Messages by Google app, you can also filter out spam. This is the default messaging app on many Android phones but if you don’t have it, you can download it from the Google Play store. 

  1. Open the Messages by Google app. 
  2. Tap the three dots in the top-right corner.
  3. Tap “settings.”
  4. Tap “spam protection.”
  5. Enable the spam protection feature under the “spam protection” settings.


  1. Open your messages app.
  2. Tap “filters in the top-left corner.
  3. Select “unknown senders.”

Turn off notifications on spam texts:

  1. Open settings.
  2. Tap notifications.”
  3. Tap messages.”
  4. Go to customize notifications and disable notifications for unknown senders.

3) Block spam messages through your mobile carrier

For extra protection from unwanted text messages, you can also filter out spam through your cell service provider. Most providers offer services that keep spam at bay. US Cellular, Verizon, AT&T, and T-Mobile, offer both free and paid options to do this, for example. 

In addition to opting in to a spam filtering service, you should also report all spam messages you receive to your service provider. If you live in the US, you can do this by copying the message and texting it to 7726. 

4) Block spam through your messaging apps

Once you’ve effectively blocked unknown numbers on your device and default messaging app, you should do the same with whatever other messaging apps you use. We’ve covered the most popular ones below. However, if you use an app we haven’t covered, we recommend checking the settings for similar options. 


Unfortunately, WhatsApp doesn’t provide any options to filter out messages from unknown senders. What you can do instead is silence unknown callers and block specific numbers that send you unwanted messages. 

To silence unknown callers:

  1. Open WhatsApp
  2. Tap the three dots in the top-right corner. 
  3. Select “settings.”
  4. Tap “privacy.” 
  5. Scroll down and tap “calls.”
  6. Enable the silence unknown callers feature. 

To block specific senders:

  1. Open WhatsApp
  2. Long press on the conversation from the sender you want to block to select it.
  3. Tap the three dots in the top-right corner. 
  4. Select “block.”


Telegram offers two options that can help you limit the number of messages you receive from unknown numbers. You can hide your phone number and restrict who can add you to groups (therefore limiting spammers who send out mass messages). 

To hide your number: 

  1. Open Telegram
  2. Tap the hamburger menu icon in the top-left corner (in the bottom-right corner on iPhone).
  3. Go to “settings.”
  4. Scroll down and tap on “privacy and security.” 
  5. Under privacy, tap “phone number.”
  6. Select “my contacts” or “nobody.”
  7. Tick the checkmark to confirm your choice (tap the back button on iPhone).

To restrict who can add you to groups:

  1. Open Telegram
  2. Tap the hamburger menu icon in the top-left corner (in the bottom-right corner on iPhone). 
  3. Go to “settings.”
  4. Scroll down and tap on “privacy and security.” 
  5. Under privacy, tap “Groups & Channels.”
  6. Select “my contacts” under “who can add me to group chats.”
  7. Tick the checkmark to confirm your choice (tap the back button on iPhone).


  1. Open Viber
  2. Tap “more” in the bottom-right corner. 
  3. Tap “settings.”
  4. Tap “calls and messages.”
  5. Scroll down and untick “receive business messages.”
  6. Go back to the previous screen and tap “privacy.”
  7. Scroll down and tap “control who can add you to groups.”
  8. Select “my contacts.”

5) Use a spam-blocking app

As an optional step, you can also download a spam-blocking app like Nomorobo or RoboKiller. These apps filter out spam and warn you about potentially malicious messages. There are a lot of spam-blocking apps out there, however. If you pick the wrong one, you could be doing more harm than good to your privacy and security. 

Before downloading any app on your phone, you should always check the data collection and sharing practices as well as the permissions the app requires. The permissions should be justifiable. For example, it makes sense that a spam-filtering app would require access to your contacts, phone app, and messaging apps. It doesn’t make sense that it would require access to your photos and videos. We also recommend you stick with reputable developers as they are less likely to compromise their reputation with sub-par privacy and security practices. 

6) Add your number to the national Do Not Call Registry

If you live in the US, you should add your phone number to the national Do Not Call Registry. This is a list, kept by the Federal Trade Commission (FTC) of numbers of US residents who don’t want telemarketers to contact them. While it won’t do much to deter scammers and other cybercriminals, it will reduce the number of marketing calls and texts you receive from legitimate companies. If any unscrupulous businesses still contact you, you can file complaints with the FTC here.

7) Remove your phone number from people search sites

One of the most effective ways to prevent unwanted messages from unknown numbers is taking your phone number and other personal information off data broker websites and people search sites. This prevents those unknown senders from getting your contact details in the first place.

Data brokers make a business out of compiling contact lists for marketers, along with relevant information such as demographic info and browsing habits to help them target you better. Both businesses and individuals use people search sites, which make your personal information publicly available, for the same purposes—with the added danger of cybercriminals mixed into the fray. Combined, they leave you exposed to swarms of marketing, phishing, scam, and other online threats. 

Removing your personal information from these sites can be challenging and time-consuming, however. This is no accident. Your personal information is valuable and these companies don’t want to give it up easily. You have two options: You can either track down which companies hold your data and ask each one individually to remove it, or you can use a personal information removal service like Incogni

If you prefer to do it yourself, check out our opt-out guides to help you start your data removal journey.

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Is it safe to open a text message from an unknown sender?

Opening a text message from an unknown sender can be dangerous. They can contain links to phishing sites or downloads that contain malware. Even if you’re aware of this, there’s always the danger of accidentally tapping on the wrong thing. It’s safest to avoid opening texts from unknown senders. 

How do I stop spam texts?

You can stop spam texts by enabling spam filtering through your device, messaging apps, and cell service provider. You can also use spam-blocking apps, add your number to the Do Not Call Registry, and use a data removal service like Incogni to prevent spammers from getting your contact details. 

How do you respond to an unknown text?

You shouldn’t respond to unknown texts. If the text is from a spammer or cybercriminal, it’ll let them know that your phone number is active and lead to more contact from them in the future. If you suspect the text is from someone you know, verify this by contacting them some other way first. 

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