House and Senate conferees have agreed on a bill aimed at preventing people from breaking into federal computers, but civil libertarians say the measure is so broad that it could be used to prosecute government whistle blowers.

Late last week the computer crime bill joined the long list of legislation that has been tacked to the catch-all government spending bill with which Congress is still fiddling. The House had passed the bill in July, as part of an anticrime package, but the computer crime provisions were stripped in the Senate because of concern about civil liberties implications.

According to knowledgeable House staffers, the bill was designed to keep criminals and so-called computer hackers from trespassing into government computers, which store an increasing amount of personal information about U.S. citizens.

The measure, sponsored by Rep. William J. Hughes (D-N.J.), would make it a misdemeanor for unauthorized users to disclose any information stored on government computers. However, civil libertarians, such as Jerry Berman of the American Civil Liberties Union, say they are worried that the distinction between "authorized" and "unauthorized" users could give the government a new way to prosecute federal employes who leak information to the press and the public.

"We think this is potentially a very broad new government secrecy statute," said Berman, the ACLU's legislative counsel. "It opens up the possibility of allowing the government to set the rules as to who has access to information."

Federal secrecy laws traditionally have focused on the content of the information itself, and whether its disclosure would harm the government. Because the bill would allow leakers to be prosecuted solely because they were not authorized to have the information, without regard to whether the information was classified or innocuous, critics say it is too broad.

The bill's supporters, however, say it is necessary to fight unauthorized entry into government computer files. A survey completed earlier this year by the inspector general of the Health and Human Services Department found 172 cases of computer fraud and abuse in 12 government agencies -- including employes who stole food stamps electronically and another who diverted benefit checks to himself.

Supporters say that government computer users who are authorized to have certain information and decide to disclose it would not be trespassing, and thus would not be affected by the new law.

As of late yesterday, opponents of the bill still hoped they could get the conferees to agree to kill it, or at least to change the measure's wording to guarantee that it remains strictly a citizen-privacy bill and not a new threat to whistle blowers.