The counter lawsuit, one of DoubleClick's multiple legal tangles in the past year, alleges that the Web advertiser used "fraudulent procurement and unlawful assertion" to receive its recently issued U.S. patent.
Last November, DoubleClick filed a lawsuit against L90 alleging patent infringement. The patent in question is related to a technology for the delivery of Internet advertising by a third-party ad server to a network of Web sites or to individual sites. DoubleClick said it received the patent last September after a two-year review by the U.S. patent office.
There's been a growing rash of patent-related lawsuits involving Internet companies. Some e-commerce companies, in a controversial practice, have patented parts of their business plans--not just their technologies.
Priceline.com is embroiled in a legal tussle with Expedia.com over Priceline's patent that allows buyers to name the prices they are willing to pay for goods or services.
Amazon.com is also jostling with rival Barnesandnoble.com over Amazon's 1-Click ordering feature. Amazon sued Barnesandnoble.com in October, claiming the online bookseller had illegally copied the e-tailer's 1-Click technology; Amazon has since won a preliminary injunction against its chief rival.
L90's complaint, filed in the Federal District Court for the Southern District of New York, asks the court to declare DoubleClick's patent "invalid and unenforceable." The company is also asking the court to end DoubleClick's alleged conduct and to award monetary and punitive damages.
"L90's counterclaims are desperate, baseless and clearly retaliatory," said Elizabeth Wang, the DoubleClick's general counsel. "This suit is clearly in response to our suit against L90 for infringement of our patent."
When applying for a patent, companies have to note whether there are others using similar methods in their businesses.
"There were a number of companies serving ads before DoubleClick filed their patent application," John C. Bohan, L90's chief executive, said in a statement. "We still feel extremely confident that these prior art examples invalidate their patent."
DoubleClick has faced several lawsuits and investigations in the past year. In March, rival 24/7 Media filed a lawsuit alleging patent infringement.
The company also has been hit with lawsuits alleging its policies violated people's privacy. In addition, DoubleClick disclosed in a filing with the Securities and Exchange Commission that it was under investigation by the Federal Trade Commission for its data-collection practices.
Just yesterday, DoubleClick appointed seven members to its recently created Privacy Advisory Board, which it hopes to use to assuage privacy concerns.
The company created the board largely in reaction to a wave of criticism by privacy and consumer groups. Their complaints stemmed from DoubleClick's $1.7 billion acquisition of Abacus Direct, a company that works with offline catalog companies.
Opponents of the merger feared DoubleClick would combine its data about surfing habits through its ad network with personal information from Abacus' transaction records.