Google says it is clamping down on ads for copycat websites that trick travellers into paying over the odds for US entry permits.
Visitors to the US must complete the Electronic System for Travel Authorisation (Esta) which costs $14 (£10.70) on the official website run by the US Department for Homeland Security.
But since Esta’s introduction in 2010, many legitimate-looking imitator sites have spawned in search rankings. Some scam users into paying as much as $80 for the same service.
After an investigation by the BBC, Google has pledged to pull down adverts that bump duplicitous sites up the rankings and earn the search giant money in the process.
The BBC sent Google several ads appearing at the top of its search results for terms such as Esta and US visa. In response Google said the ads broke its rules and would be removed.
In a statement to the corporation it explained: "We have policies that prevent ads for paid products or services that are available from a government or public source for free or at a lower price, unless they offer a clear added value."
On why the official Esta website does not appear more prominently in its rankings, Google said its search results were determined by algorithms.