What is the rationale of SMS verification in free wifi hotspots in airports?

Question

I recently visited a few airports, although most of them had standard wifi which allowed access after a landing page, I have noticed that some free wifi providers (Shanghai Pudong, Singapore Changi) have began to request for a random password to be sent to your mobile phone via SMS, after which your device will be allowed access. I was not charged by my mobile phone provider for either the SMS or the access.

Is there a meaningful rationale for why they are doing this? After all, sending long-distance international SMS certainly has a significant non-zero cost, and I don't see any obvious benefit in them doing this.

Answer 1

I can think of a few reasons:

1. Verifying the identity of Wi-fi users, in case a court subpoena comes in requesting information about a certain user. It's not a bullet-proof method (many countries offer anonymous sim-cards), but it's probably good enough in most cases. Some countries may also ban fully anonymous Wi-fi (such as Germany or Turkey).

2. Making sure they can cut-off users who use too much traffic or time (some free connections are limited to 15/30/60 minutes). It becomes harder to reconnect once banned since changing your MAC address is not sufficient.

3. Denying access to long-term users. It's often possible for local residents to connect to major Wi-fi hubs close by.

4. Maintaining accurate statistics on the number of users/their country of origin/etc.

5. Showing targeted advertisements based on your phone number.

6. Having a database of phone numbers for future text advertisements/sales calls/etc. It's probably hidden away somewhere in the long "Terms and Conditions" that nobody reads.

Answer 2

For Singapore, it is because of the law---they want to be able to track you down if necessary.

It is the same even when you are trying to buy a S$15 prepaid phone card---you need to give your identification number (either your National Registration Identification Card number or some other number if you're a foreigner) and the seller needs to record it down. Again, so that you can be tracked down if necessary.

Ostensibly in case you issue terrorist threats and the like. But of course conveniently enough, your information can be used for other purposes. Singapore isn't exactly a land where privacy is prized.

I do not know about other countries, but my guess is that in China it is for similar reasons.