WASHINGTON (Reuters) - U.S. law enforcement leaders said on Wednesday that computer attacks were one of the fastest-growing areas of crime and that continually updated technology made it nearly impossible to keep track of the problem.

Addressing a Senate subcommittee on Internet security, Attorney General Janet Reno said last week's attacks on major commercial Web sites showed how important it was for the United States to devise a coordinated strategy against cyber-crime.

``How we deal with cyber-crime is one of the most critical areas we face,'' said Reno.

She called for a five-year plan to deal with the issue and said computer equipment needed to be standardized as continually updated technology meant the costs of resolving the problem were extremely high.

``We need a means of ensuring uniform standards in respect to equipment and technology. It is becoming obsolete practically before we get it installed and the costs can be astronomical,'' said Reno.

In addition, Reno said tougher penalties needed to be imposed on cyber attackers to deter them from causing havoc on the Internet.

Commenting on last week's attacks on Web sites such as Yahoo! ( NasdaqNM:YHOO - news), eBay (NasdaqNM:EBAY - news) and Amazon.Com (NasdaqNM:AMZN - news), Reno said computer crime investigators were working around the clock to catch the perpetrators.

``At this point I would simply say that we are taking the attacks very seriously and that we will do everything in our power to identify those responsible and bring them to justice,'' Reno said.

FBI Director Louis Freeh said he was pleased with the progress made in the investigation so far.

``There are fast-developing leads as we speak,'' he said, adding that the investigation was being conducted in the United States and in countries such as Germany and Canada.

Significant Threat To U.S. Security

Cyber-crime posed a significant threat to national and economic security in the United States and the FBI's case load had increased dramatically in recent years, Freeh said.

The FBI said it opened 547 ``computer-intrusion cases'' in 1998 and this number more than doubled to 1,154 in 1999.

``In short, even though we have markedly improved our capabilities to fight cyber intrusions the problem is growing even faster and we are falling further behind,'' Freeh said.

Threats ranged from simple hacking conducted by juveniles and disgruntled employee attacks to sophisticated intrusions that the FBI feared were sponsored by foreign powers.

``Computer crime is one of the most dynamic problems the FBI faces today. Just think about how many computers you have owned and how many different software packages you have learned over the past several years and you can only begin to appreciate the scope of the problem we are dealing with in the fast-changing era, '' said Freeh.

Representatives from several companies also addressed the subcommittee and urged the government to take action to curb cyber-crime.

Robert Chestnut, associate general counsel for eBay, said last week's attack on his company's Web site appeared to be well-planned and affected the site on a huge scale.