What is a call blocker? The ultimate guide to stopping unwanted calls

What is a call blocker?
The ultimate guide to stopping unwanted calls

Unwanted phone calls, including spam, telemarketing and scam calls, remain a persistent global issue affecting mobile users worldwide. These intrusive communications range from nuisance calls to sophisticated scams, often using fake numbers and automated dialing systems to bypass traditional blocking methods. With advancing technology enabling more elaborate caller ID manipulation, effective call blocking solutions have become increasingly essential for both personal and professional communications.

How a spam call blocker works and why KnownCalls outstands

Spam calls aren’t just annoying – they can be dangerous. Scammers use fake numbers to:

steal personal information (phishing);
trick victims into payments (tech support scams);
harass business and public figures.

According to the article in Business Wire and the report by Hiya (a company that provides voice security and identity services) in the first half of 2024, nearly 20 billion calls were flagged as suspected spam. Which means more than 107 million spam calls every day. Of those unknown calls (calls coming from outside a person’s contact book) 22% were determined as nuisance and 7% as fraud.

In the first quarter of 2025, Hiya detected 12.5 billion suspected spam calls. Among them 24% were identified as nuisance and 9% as fraud calls.

There’s also an increase in AI deepfake scams, which impersonate people and/or organizations using AI-generated voice-cloning technology. All this means the problem of unwanted calls is constantly growing and changing its forms.

But don’t worry! There’s an easy way to deal with cold calls and any other unwanted calls. A call blocker is a solution you need.

In this guide we’ll explain:

What is a call blocker and how it works
Why KnownCalls is different from other apps
Who should use it (and who shouldn’t)
How to stop spam calls for good

What is a call blocker?

A call blocker is an app or service that prevents unwanted calls from reaching your phone. It helps prevent calls from specific numbers, unknown numbers, or even entire area codes. A call blocker can also identify and filter robocalls and spam calls. It doesn’t affect your ability to make outgoing calls.

There are different ways of blocking unwanted calls depending on your phone and carrier.

Types of call blockers:

Built-in features of your phone. Many smartphones, including Android and iOS, can block incoming calls from specific numbers out of the box. You can block numbers manually by adding them to a black list, though there may be a limit on how many numbers you can add.
Standalone devices. Some landline phone providers offer a special device to their clients that allows them to block unwanted incoming calls.
Apps. Today app stores got hundreds of call blocking apps for both Android and iOS.
Software. Various enterprises often use VoIP phone systems with built-in protection from nuisance calls.

A call blocker app on your mobile phone is one of the best ways to protect yourself from nuisance calls.

How a call blocker works

A call blocker works like a filter. Usually there are online databases gathered from users’ reports which help apps decide if an incoming call is a scam, a spam, a robocall, etc. Then the app hinders the call from reaching you. Some apps let you choose whether to respond to calls marked as scams. There are apps that can protect you from unwanted text messages as well.

There is a multitude of available call blockers. Some of them are free, others offer their services for a price.

What makes KnownCalls so different from other apps?

Many call blockers fail because:

they rely on outdated crowdsourced spam databases;
they still let the phone ring before blocking the calls;
they sell user data to advertisers.

Learn what a call blocker is with KnownCalls

KnownCalls takes a smarter approach and fixes this with its key features:

No calls from any unknown numbers. The app lets only your trusty contacts to get through, leaving you free to communicate with people that really matter to you.
No Internet needed. KnownCalls works offline, so scammers won’t be able to disturb you when you’re you’re taking a break from the World Wide Web.
No storing or sharing of your data. You may not worry about your privacy since its protection is our strongest commitment.
No ads or hidden fees. KnownCalls is totally free for all users.

The app uses a simple but powerful principle: “If the number isn’t in your contacts – Block it.” That’s why, unlike traditional blockers that miss new spam numbers, KnownCalls guarantees 100% protection from nuisance calls.

Who should use KnownCalls?

Business professionals (avoid spam without losing clients)
Public figures (block suspicious strangers while staying reachable)
Parents (protect kids from unknown callers)
Seniors (don’t let scammers exploit your trust)
Anyone who hates spam calls

Please note! KnownCalls may not suit you if you want to answer unknown calls (for instance, deliveries).

One of the greatest advantages of KnownCalls – the “cumulative effect”.

Most spammers delete inactive numbers from their lists. Since KnownCalls drops calls instantly instead of silencing them, after some time scammers will think your number is dead – so they will stop calling altogether.

Want to install and use KnownCalls?

Download it from the Google Play Store.
Open the app and enable call blocking with one tap.
Done! Now only contacts can reach you. Enjoy!

Important tip: add important numbers (doctors, couriers) to your contacts to avoid blocking them.

Final verdict: the best free spam call blocker

If you only answer calls from known contacts, KnownCalls is the most secure, private, and effective call blocker available. With our app you’ll reduce interruptions during work and important meetings. And you can be sure that senior members of your family won’t be defrauded.

Just install KnownCalls and enjoy the sense of security and peace of mind!

June 24, 2025