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SMS Flooding Filter

SMS Flooding Filter

Profile Headshot of Mehak Dhingra
Mehak Dhingra

3
mins read

March 10, 2025

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Key Takeaways

SMS flooding occurs when a large volume of text messages is sent in a short period, often disrupting services or spamming users. 

An SMS flooding filter helps detect and prevent such excessive messaging by monitoring traffic patterns and enforcing rate limits. Businesses and service providers use these filters to maintain smooth communication and protect users from unwanted messages.

What is SMS Flooding Filter?

An SMS flooding filter is a security measure designed to prevent an excessive number of text messages from being sent to the same recipient within a short timeframe. These filters help safeguard users from spam messages that could disrupt their devices while also protecting SMS API providers and mobile networks from potential service overloads.

SMS Flooding Prevention Mechanism

Here are some ways to prevent SMS flooding

  1. Traffic Monitoring

Limits SMS traffic to six identical or 20 varied messages per recipient within an hour to prevent excessive messaging.

  1. Throttling & Rejection

Once the limit is exceeded, messages are either delayed or blocked to protect both users and the platform.

  1. Minimizing Impact

Prevents overwhelming recipients and safeguards the stability of the SMS API.

  1. Rare Triggering in Normal Use

Typically, legitimate traffic doesn’t activate the filter, ensuring smooth operations.

  1. Common in Testing

Developers may trigger the filter unintentionally when testing applications or due to coding loops.

  1. Credit Protection

Helps prevent accidental depletion of SMS credits from unintended high-volume messaging.

SMS Flooding Filter Errors

  1. Error Code 5020

If a message is rejected due to the flooding filter, indicated by error code 5020, you should pause sending messages to that recipient until they fall within the allowed limits again.

  1. Message Delivery Not Guaranteed

The filter may not always block multiple messages and once delivered, refunds cannot be issued.

  1. Customer Responsibility

It is essential for users to thoroughly test their code before deploying to production.

How Does SMS Flood Attack Work?

Here’s how SMS flood attack work

  1. Automated Message Generation

Attackers use bots or software to submit a large number of requests through a website's contact form, filling the phone number field with fake or random entries. 

  1. Server Overload

The website's server receives and processes these excessive requests, attempting to handle each as a legitimate business text message.

  1. Performance Impact

The surge in traffic can slow down or crash the server, potentially causing service disruptions for genuine users.

  1. Financial Strain

High-volume requests can lead to increased data usage, unexpected charges and other financial consequences for the website owner.

Potential Impact of an SMS Flood Attack

SMS flood attacks can severely affect businesses, resulting in productivity losses, financial damage and reputational harm. To safeguard against such threats, organizations must implement strong cybersecurity measures. The consequences of these attacks may include

  1. Degraded Website Performance

Excessive traffic can overload servers, leading to slow response times and high resource consumption.

  1. Data Exposure & Trust Issues

User information may be compromised, eroding customer confidence.

  1. Security Breaches & Fraud

Attackers may exploit vulnerabilities for account takeovers and unauthorized transactions.

  1. Operational Disruptions

Business processes can be interrupted, affecting overall service reliability.

Conclusion

By monitoring message patterns, enforcing rate limits, and blocking suspicious activity, businesses can protect their users and infrastructure with the help of SMS flooding filters. Proper implementation ensures seamless communication while preventing spam and fraud. Regular monitoring and testing of these filters help maintain system integrity and reliability.

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