SpamBlocker: How to Block Spam Calls and SMS on Android

Spam calls and unwanted text messages have become a daily headache for almost everyone with a smartphone. From persistent telemarketers to dangerous scam calls, these interruptions break your focus and invade your privacy. While many call blocker apps promise a solution, most of them demand full access to your contacts, display intrusive ads, or force you to replace your favorite phone dialer and messaging apps.

In this blog post, we are taking a deep dive into SpamBlocker, a popular open-source Android tool created to solve this exact problem. You will learn what SpamBlocker is, how its unique features protect your phone, what your device needs to run it, where to download it safely, step-by-step instructions for installation and usage, common troubleshooting solutions, FAQs, and author credits.

What is SpamBlocker?

SpamBlocker is a free, lightweight, privacy-focused Android application designed to filter out unwanted phone calls and SMS messages automatically. Created by developer aj3423, the app is hosted publicly on the SpamBlocker GitHub Repository.

Unlike standard call blocking apps on the Google Play Store, SpamBlocker does not collect your personal data or upload your contact list to private servers. It operates as an underlying system filter using native Android APIs. This means you do not have to replace your stock phone dialer or SMS app (such as Google Messages or Samsung Phone). SpamBlocker intercepts incoming calls and text notifications quietly in the background according to rules that you control.

Features of SpamBlocker

SpamBlocker offers a wide range of smart filters and customization tools that go far beyond basic blacklists. Here are the core features you can use:

• Contact and Group Whitelisting: Easily allow calls from saved contacts, specific contact groups, or whole number ranges by matching contact prefixes.
• STIR/SHAKEN Verification: Automatically detects and blocks spoofed phone numbers that fail network-level caller authentication standards.
• Repeated Call Bypass: Allows emergency or important calls to get through if the same number dials you multiple times in a short time frame.
• Dialed and Answered Memory: Automatically whitelists numbers you have previously called or answered so you never miss a legitimate return call.
• Emergency Call Override: Temporarily disables blocking rules after you place an emergency call (such as dialing 911), ensuring emergency responders can call you back.
• Smart Push and SMS Alerts: Temporarily allows incoming calls after you receive specific text messages or app notifications (for example, delivery drivers or ride-share updates).
• OTP Flood Protection (SMS Bomb): Detects and blocks continuous waves of unwanted OTP or verification codes.
• App-Based Rules and Meeting Mode: Can allow calls when specific apps are currently in use, or automatically decline calls during online video meetings.
• Off-Time and Calendar Schedules: Automatically turns blocking rules on or off based on your work calendar, sleep schedule, or specific hours of the day.
• Regular Expressions (Regex): Advanced users can create custom regular expression rules to match complex number patterns or text content.
• Offline Spam Database Integration: Download and import crowd-sourced databases (like the FTC Do Not Call list) directly onto your phone for instant local blocking.
• Privacy-First Design: All offline features process data locally on your device with zero data harvesting.

Requirements

Before installing SpamBlocker, make sure your Android device meets the following requirements:

• Operating System: Android 10 or higher (API level 29 and above). Older Android versions are not supported.
• Storage: Around 10 MB to 20 MB of free storage space for the app and local database downloads.
• Permissions: Depending on the features you want to enable, SpamBlocker may request optional permissions including Default Caller ID access, Notification Listener access, Contacts read access, Call Log access, SMS read access, and Battery Optimization exemption.

Download

Because SpamBlocker is open-source software, you can download it from several trusted platforms:

1. GitHub Releases: You can download the latest official APK file directly from the SpamBlocker GitHub Releases Page.
2. Obtainium: If you prefer automatic background updates directly from GitHub, you can add the GitHub repository link to Obtainium.

Using F-Droid or Obtainium is recommended because these platforms keep the app updated automatically without requiring manual APK installs.

How to Install

Installing SpamBlocker takes only a few minutes. Follow these simple steps:

1. Download the File: Grab the latest .apk file from GitHub or search for “SpamBlocker” in your F-Droid client.
2. Enable Unknown Apps (If installing via APK): If downloading directly from your web browser, tap on the downloaded file. When prompted by Android, enable permission to install apps from unknown sources for your browser.
3. Tap Install: Confirm the installation prompt and wait for the process to finish.
4. Open SpamBlocker: Launch the app from your app drawer to begin the initial configuration setup.

Check this also: Fossify Documents

How to Use

Setting up SpamBlocker requires configuring two primary system settings on Android:

1. Set Up Call Screening

• Open SpamBlocker and navigate to the initial setup screen.
• Go to your Android phone Settings > Apps > Default Apps > Caller ID & Spam.
• Select SpamBlocker as your default Caller ID and Spam app.

2. Set Up SMS Screening

• Open SpamBlocker settings and grant Notification Access when prompted.
• Because SpamBlocker filters text messages by inspecting incoming notification content, go to your main SMS app settings (like Google Messages) and disable default SMS notifications.
• SpamBlocker will now generate clean notifications only for messages that pass your filters, avoiding duplicate alerts.

3. Configure Your Filtering Rules

• Navigate to the Filters tab inside SpamBlocker.
• Enable basic default rules like Contacts (allows callers saved in your phonebook) and Repeated Calls (allows urgent callbacks).
• Optional: Go to the Database section to download an offline blocklist (such as FTC-DNC) or add custom block rules using phone number prefixes.

Once configured, SpamBlocker works quietly in the background. You can close the app interface, and Android will continue enforcing your rules automatically.

Troubleshooting

Here are solutions to a few common issues users might encounter:

• App Stops Blocking After Swiping Away: Android battery optimization may kill background services. Open your device Settings > Battery Optimization, search for SpamBlocker, and select “Don’t Optimize” or allow background activity.
• Duplicate SMS Notifications: This happens if both your default SMS app and SpamBlocker are displaying alerts. Turn off notifications inside your standard SMS app settings so SpamBlocker can manage notifications exclusively.
• Play Protect Security Warning: When installing directly from an APK file, Google Play Protect may display a warning because the APK was signed independently outside the Play Store. You can safely click “Install Anyway” after verifying the file source, or install via F-Droid instead.
• Missed Call Notifications on Android 16+: On newer Android versions, silenced or blocked calls may still generate a native system “Missed Call” notification. This is default system behavior introduced in recent Android versions and does not mean the call rang through.

FAQs

Credits

SpamBlocker is actively developed and maintained by lead developer aj3423, along with an active community of open-source contributors on GitHub who assist with code improvements, translation updates, and bug fixes.

The full project code, license details, and issue tracking are publicly available on the official aj3423 SpamBlocker GitHub Page.

Conclusion

SpamBlocker is one of the most reliable, customizable, and privacy-respecting call and SMS blocking solutions available for Android today. By leveraging native Android APIs and powerful offline filtering rules, it keeps unwanted telemarketers and scammers away without forcing you to sacrifice your personal data or change your favorite messaging apps. If you are tired of daily spam interruptions, giving SpamBlocker a try is a fantastic choice.

Have you tried SpamBlocker on your phone yet, or do you have any questions about setting up your filtering rules? Please leave a comment below and share your thoughts with us!