Block consecutive calls within a defined time window

[milanogc]

The feature

Ability to block consecutive calls within a defined time window if the previous call was blocked.

Problem

In Brazil, fraudsters often use phone numbers with common prefixes, which SpamBlocker already blocks effectively with regular expression rules. However, after these calls are blocked, the fraudsters switch to completely different numbers.

They seem to use automated telephony systems that can place calls very quickly, one after another, with different numbers. This makes it harder to rely only on prefix or pattern-based blocking rules, because the incoming numbers vary significantly.

Expected behavior

• If a call is blocked, any subsequent call received within X seconds (e.g., 60s) should also be blocked automatically
• After each blocked call, the timer resets
• Calls explicitly allowed by other rules (e.g., contacts) should not be blocked, even within this time window

Possible naming

• "Consecutive Call Blocking"
• "Block Calls in Sequence"

[aj3423]

Sounds like you don't want to block all unknown numbers with .*, otherwise this won't be a problem, which also means some unknown numbers can be valid and useful to you. But with this feature enabled, those valid unknown numbers will also be blocked. It does more harm than good to me.

Perhaps you're using the "Reject" blocking mode, it rejects calls immediately, so spammers would know it's been blocked. Try the "Silence" mode instead, it extends the call duration, spammers typically won't try again after waiting for 20 seconds.

[hollownights]

I’ve thought about something like this before, but it only makes sense when you are trying to use the app in a way to NOT block most calls, and this is different from the app’s implied usage. Like @aj3423 (sorry for the repetition) implied, even when the “Contacts” function is set to “Lenient,” there is this thought that at some point/priority you are going to introduce a “.*” number block rule to block anything that has not been allowed by other rules. I don’t think this is a straightforward thought, but it is how the app is supposed to work.

What you are proposing would be a “calls burst blocking” that, when using the app more to allow than to block, would (like you suggested) block any further calls, from any number, after a call from a “specific” number has been blocked (“specific” because it would come from a number for which there is a regex, or that is in the spam database, or was flagged by an API as spam). Different from what you proposed, though, the timer should not be “reset” with each new blocked call, but rather initiated with each call blocked for matching regex/database/API (this is the behavior for the “Emergency” function). Resetting the timer would deactivate the block, not (re)initiate it.

For now, try what @aj3423 suggested and change the “Block type” from “Reject” to “Silence,” but also consider adding a Query API, like Tellows.

[milanogc]

I tested the "Silence" mode as suggested, but unfortunately it didn’t improve the situation. During my test period I still received up to 7 calls within the same minute.

What I’m proposing is a feature to block calls that arrive very close in time and are most likely part of a call burst from an automated system. I understand this involves the risk of blocking a valid call, but in my case this is a trade-off I would personally accept.

I also checked Tellows, but these numbers are not recognized as spam there either, which makes prefix/pattern blocking or external APIs less effective in this scenario.

That’s why I still believe a feature like the one I suggested could add value.

[aj3423]

I see, then I'll add it.

Here's the proposal:

• A new feature "Consecutive Call" in quick settings, when activated, it changes the default behavior "allow by default" to "block by default", a call that passes all rules will be blocked.

  • It can be activated after:
    • A call is blocked
    • A call is answered, but the call duration is less than X seconds
  • When activated, an undetermined call will be blocked, and the timer will be reset

• Options in the popup dialog:

  • Expire Duration, 30 seconds by default.
  • Activate by blocked call?
  • Activate by answered call?
    • With a call duration inputbox

How do you think?

[milanogc]

This is perfect! The "answered but less than X seconds" is awesome! Great idea! Thanks!

[aj3423]

Well, today I got another feature request #409
They are very similar, one for calls and one for texts. The only difference is the activate strategy

• this feature is activated by blocked calls
• that one is activated by text from the same number

I think this feature will be implemented in the debouncing way, I'll need more time to think about it.

[aj3423]

done: https://github.com/aj3423/SpamBlocker/actions/runs/17347764042

You can find it in the workflow presets, the "Call Throttling", it should work out of the box, no need to change anything.

[milanogc]

Awesome, @aj3423 ! It’s my first time trying out the workflow feature. I’ll give it a try and share feedback in a few days.