Last week a U.S. court ruled that federal agents do not need a search warrant to monitor the computer and Internet use of a suspect.
In a drug case from San Diego County, the Ninth U.S. Circuit Court of Appeals in San Francisco likened computer surveillance to the "pen register" devices that officers use to pinpoint the phone numbers a suspect dials, without listening to the phone calls themselves.
The U.S. Supreme Court upheld the use of pen registers in 1979, saying callers have no right to conceal from the government the numbers they communicate electronically to the phone companies that carry their calls.
Federal law requires court approval for a pen register. But because it is not considered a search, authorities do not need a search warrant, which would require them to show that the surveillance is likely to produce evidence of a crime.
They also do not need a wiretap order, which would require them to show that less intrusive methods of surveillance have failed or would be futile.
In Friday's ruling, the court said computer users should know that they lose privacy protections with e-mail and Web site addresses when they are communicated to the company whose equipment carries the messages.