It was unclear why Symantec waited until now to reveal the patents, which were granted last year. A representative at rival McAfee said McAfee had not known of the patents and is looking into the matter.
The patents guard a key component of Symantec's Norton AntiVirus 5.0, 2000, and 2001 products, which the company calls its "microdefinition system" and which allows data that is updated frequently to be efficiently patched.
"When there is a lot of content that has to be updated regularly, this can be handy," said Carey Nachenberg, chief researcher for the Symantec AntiVirus Research Center and one of the patent holders. "When you have so many updates, it is unaffordable and inefficient to post thousands or millions of patches."
The debate over software and business patents has heated up over the last 18 months.
In October 1999, online bookseller Amazon.com sued rival Barnes & Noble for infringing on its patent on buying books with a single click of the mouse. Later, Amazon grabbed patents for a recommendation service and an affiliate program. Then, Amazon CEO Jeff Bezos and Tim O'Reilly, Amazon's most influential critic and the founder of technical publisher O'Reilly & Associates, helped form a service that offers rewards for evidence that a patented technology had been used prior to the date the company filed its patent.
According to the company, the ability to update virus definitions and software a piece at a time can result in smaller downloads--sometimes up to 90 percent smaller. That means the company's LiveUpdate software can run up to four times faster than if it had to download the full virus definition.
Symantec is not only attempting to apply the patents to the antivirus industry but also to the software industry as a whole. In its statement Wednesday, the company noted that "the technology may be used to update general computer readable files, which may include data files, program files, database files, graphics files, or audio files."
Yet incremental updates have been around for a long time, most likely for longer than the Internet has been around.
Software companies that need to fix buggy applications would rather not force people to download an entire new program. They'd rather enable customers to download a small update.
Nachenberg said such software updating is old hat, but the way Symantec does its updates is different.
"If you think about virus definitions, they are an entirely different problem (than software)," he said, adding that the major difficulty is that virus definitions change so often. The company's logging of new viruses can easily lead to a new update every day. "I have to be able to patch from any of what could be 365 (definition) updates in a year."
At least one competitor in the antivirus industry said Symantec's new patents were not a worry.
"We do incremental updates; we've been doing it for a long time," said David Perry, global director of education for antivirus company Trend Micro. "We have our own technology, so we are covered."