Google has opted for litigation to patch up its problems preventing rogue online pharmacies from securing AdWords services.
"As we identify additional bad actors, we will add them to the lawsuit," Michael Zwibelman, Google litigation counsel wrote on the company's blog.
Zwibelman believed litigation would act as a deterrent to the practice, which was the subject of a major US crackdown.
Google's decision came just days after it was revealed that US domain name wholesaler eNom had acquired the services of LegitScript to weed out rogue online pharmacies.
eNom had previously resisted requests to take down the websites of the rogue pharmacies unless it was issued a court order or law-enforcement directive, according to a Financial Times report.
Google compared rogue pharmacy customers to "malware ads" and blamed their growing sophistication for the advertising giant's inability to stop them violating its policies.
"Despite our best efforts-from extensive verification procedures, to automated keyword blocking, to changing our ads policies-a small percentage of pharma ads from these rogue companies is still appearing on Google," said Zwibelman, noting the company had "struggled with this problem for years."
"It's been an ongoing, escalating cat-and-mouse game -- as we and others build new safeguards and guidelines, rogue online pharmacies always try new tactics to get around those protections and illegally sell drugs on the web."
US authorities have stepped up efforts against rogue online pharmacies.
The Department of Justice earlier this month indicted 11 people in connection with rogue pharmacies that collectively netted its operators US$80 million (AU$83 million).