Singapore has passed strict new legislation to protect the country's computer systems from attack.
Singapore has witnessed rising computer crime in recent years
The government has said the legislation was necessary because of the damage that computer hacking can cause.
The laws allow the monitoring of all computer activity and "pre-emptive" action, though an official said they would be used "sparingly".
Some members of parliament said the measures could be open to abuse, with threats to individual liberty.
Singapore's Senior Minister of State for Law and Home Affairs, Ho Peng Ke, said the law aimed to fight "cyber terrorism."
He said it would be used mainly against threats to national security and essential services like banking and finance.
"Instead of a backpack of explosives, a terrorist can create just as much devastation by sending a carefully engineered packet of data into the computer systems which control the network for essential services, for example the power stations," Mr Ho said.
The new law allows police to take "pre-emptive action" to protect computer networks from unauthorised entry by hackers.
Those found guilty of hacking or defacing a web site could get up to three years in jail, or be fined up to $5,800.
The government has said the measures are necessary because of rising cases of successful hacking - there were just 10 in 2000, but that had risen to 41 last year.
Singapore has been tightening security since last year's Bali bomb attacks in neighbouring Indonesia.
But some MPs said the new law was another aspect of the city state's authoritarian side.
Chin Tet Yung, chairman of the Government Parliamentary Committee for Home Affairs and Law, said that it could become, "an instrument of oppression itself."