> it's trivial to rotate between 30 or 40 WiFi networks even before you get into mobile SIM swapping software
All WiFi networks that are easy to hack into and are frequently used by spammers - you can automatically blacklist: every time you ban spam account - you should also ban the IP network that facilitated in this spam account creation.
> SMS authentication costs a significant amount of money for a service to provide
Sending SMS in the US starts from $0.0079 However I see that in other countries sending SMS is [10x?] more expensive. So I guess SMS is not a good solution for, say, Vietnam, which IP networks Dreamwidth blacklists.
But I see that Twilio's solution will not cover the most problematic countries such as Vietnam.
I guess that Dreamwidth solution for new accounts Vietnam, could be carefully monitored invitation system.
Another component of monitoring - reports from well-established Dreamwidth users. If old Dreamwidth user friended the new account - it is a good sign. If old Dreamwidth user banned the new account - it is a bad sign and Dreamwidth may automatically delete such new account. Especially if this new account was created from low quality IP network.
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All WiFi networks that are easy to hack into and are frequently used by spammers - you can automatically blacklist: every time you ban spam account - you should also ban the IP network that facilitated in this spam account creation.
> SMS authentication costs a significant amount of money for a service to provide
Sending SMS in the US starts from $0.0079
However I see that in other countries sending SMS is [10x?] more expensive.
So I guess SMS is not a good solution for, say, Vietnam, which IP networks Dreamwidth blacklists.
> toll fraud and pumping
The first article on SMS pumping fraud I found - describes the solution as well:
https://support.twilio.com/hc/en-us/articles/8360406023067-SMS-Traffic-Pumping-Fraud
But I see that Twilio's solution will not cover the most problematic countries such as Vietnam.
I guess that Dreamwidth solution for new accounts Vietnam, could be carefully monitored invitation system.
Another component of monitoring - reports from well-established Dreamwidth users.
If old Dreamwidth user friended the new account - it is a good sign.
If old Dreamwidth user banned the new account - it is a bad sign and Dreamwidth may automatically delete such new account. Especially if this new account was created from low quality IP network.