In article , Eric Stevens
wrote:

After years of using my card around Auckland (NZ) I flew to Geneva
(Switzerland) to visit my daughter. My bank got all twitchy when I
used my card to withdraw some cash in Geneva. They seem to be watching
for changes in the pattern of card use.

That may be part of their algorithm.

Yes. Now when I'm going overseas I ring them up and tell them. Their
idea.

some card issuers determine that automatically, such as from purchases
of airline tickets and/or hotel reservations in the destination
country.