Imagine a SMS flood using a few phone numbers. The client blocks the phone numbers using the build in mechanism of the smart phone, and thus does not receive any notifications. Even though the user blocked the messages on his or her cell phone, does the SMS flood still cause a denial of service for SMS messages from other numbers? Or, does the blocking completely prevent the flood from those numbers from causing any harm? How does this work?

From an IP perspective, a few servers can take down a single server, especially a home connection. Even when the packets are blocked with IPTables, the service is still completely unreachable because it's flooded at the network layer. I know that SS7 is very different..For one thing, it's connection based, instead of packet based.

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    what kind of blocking?
    – schroeder
    Commented Nov 2, 2017 at 15:00
  • "still cause" - does an SMS flood cause a DoS? If so, what kind? I'm thinking that the answer here is self-evident.
    – schroeder
    Commented Nov 2, 2017 at 15:02
  • Well, when the user does not block the number, there is clearly a denial of service because there are so many sms messages, and they arrive faster than can be deleted, so the user is unable to access legit sms messages, and the phone battery drains faster. However, I'm not sure how exactly does this work. Is the blocking client sided? Is the network actually congested or just the phone? Commented Nov 2, 2017 at 15:07

1 Answer 1


There are different kinds of blocking. The DoS you describe is merely a UI-based problem.

If blocked from the SMS app, then the incoming SMS is ignored and not displayed. This happens client-side. Which means there might be congestion in the network, but SMS is not meant to have high QoS, so you might never notice a problem. But it does solve the UI-based 'DoS' problem. Other SMSs from other numbers would never be affected anyway at the network level.

If reported to your carrier, then the blocking happens at the network level.

SMS flooding is different from IP network based flooding. SMS clients do not have direct access to the network, they are clients of the network, so that regulates a lot.

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