A DoubleClick (dclk) spokesman confirmed a report in The Wall Street Journal on Friday that the company had to shut down some of its servers to investigate the attacks. He said DoubleClick customers had not been able to access some of its services during the shutdown.
The disruption was minimal, the spokesman said, although he was unable to say how long the system checks would continue.
An article on a Paris-based Web site, Kitetoa.com, first highlighted the problem, which DoubleClick said it was taking very seriously.
"While the attempt to access our systems appear to be mischievous in nature we take seriously any attempt to compromise the security of our systems," Jules Polonetsky, the company's chief privacy officer, said in a statement. "We do not believe that there has been any serious impact to our networks but we are working aggressively to ensure the integrity of our systems," he said.
DoubleClick also said Friday that it had won a class-action suit regarding its privacy policies in U.S. District Court in the Southern District of New York. The suit alleged that the company's practice of putting electronic cookies' on individual's computers broke several state and federal laws. It was dismissed by Judge Naomi Reice Buchwald.
In January, the Federal Trade Commission dropped its inquiry into the company's privacy issues. The investigation began after an uproar from privacy advocates alarmed by DoubleClick's plans to merge the names of its anonymous users and their Web-surfing activities with personally identifiable information from its Abacus Direct offline database unit.
DoubleClick recently said would cut 10 percent of its work force and restructure its media business to combat a slowdown in the ad market.