It doesn’t looks like an IMSI-Catch attack, much more it seems to be a miss configuration, someone playing around with YateBTS in his/her laptop plugged with a BladeRF, completely forgotten to disable or modify source to avoid the SMS welcome, so everyone who walks in the RSA conference close to this YateBTS station received a welcome SMS as showed above.

@s7ephen tweet about this message:

David Burgess (the man who started the OpenBTS project time ago with Harvind Samra) wrote his own note from YateBTS web page regarding this extrange rogue tower:

The ‘rogue GSM tower’ episode and Cambridge Analytica: why ethics matters to technology

Probably this RSA edition will be remembered for the attendees data leak (article from theregister.co.uk), but is also quite interesting this GSM station broadcasting welcome SMS.

Pedro