Rob Copeland and Katherine Bindley:

Yet despite its powerful algorithms and first-rate software engineers, the company struggles to protect against chronic deceit on Google Maps.

Once considered a sleepy, low-margin business by the company and known mostly for giving travel directions, Google Maps in recent months has packed more ads onto its search queries. It is central to Google parent Alphabet Inc.’s GOOG 0.93% hope to recharge a cresting digital-advertising operation.

Often, Google Maps yields mirages, visible in local business searches of U.S. cities, including Mountain View, Calif., Google’s hometown. Of a dozen addresses for personal-injury attorneys on Google Maps during a recent search, only one office was real. A Viennese patisserie was among the businesses at addresses purported to house lawyers. The fakes vanished after inquiries to Google from The Wall Street Journal.

The false listings benefit businesses seeking more customer calls by sprinkling made-up branches in various corners of a city. In other cases, as Ms. Carter discovered, calls to listed phone numbers connect to unscrupulous competitors, a misdirection forbidden by Google rules but sporadically policed by the company.

Hundreds of thousands of false listings sprout on Google Maps each month, according to experts. Google says it catches many others before they appear.

Online advertising specialists identified by Google as deft fraud fighters estimated that Google Maps carries roughly 11 million falsely listed businesses on any given day, according to a Journal survey of these experts.