Michael Vatis, director of the FBI National Infrastructure Protection Centre (NIPC), urged businesses to abandon their usual reticence and to begin exchanging information with the police and government agencies.
The plea came as the NIPC issued new warnings that businesses are facing another round of denial of service attacks which wiped millions of share prices earlier this year.
"Industry needs to be more willing to work with government," he said, "Our principle need is to get information. We can't issue warnings unless we get information about threats. The best source of information is private companies."
Vatis identified the Internet as the greatest IT security threat, and urged companies to place pressure on suppliers to improve the security features of their products.
"Manufacturers respond to market demands. The market has to demand better levels of security built into their products," he said, speaking at the World E-commerce forum.
The NIPC has gathered evidence that hackers are planning a denial of service attacks that blighted Amazon and eBay earlier this year, within a matter of months.
But Vatis said that businesses had been slow to react to similar warnings in the past.
Companies were failing to make use of software posted on the NIPC Web site which detects the tools used by hackers for the denial attacks, he said.
The NIPC was set up four years ago to gather intelligence on computer crime, share information with the private sector and to provide training to other law enforcement agencies on computer crime. It has a budget of $14m a year.