The hacktivist collective Anonymous is threatening supporters of the Cybersecurity Information Sharing Act (CISA), warning that they should drop it if they "value the sanctity" of their loved ones and themselves.
The US bill has prompted privacy concerns because of its intention to authorise sharing of information between companies and government agencies, and is due to be put before a senate intelligence committee next month.
In a video posted YouTube, Anonymous said: "Not only is this a direct attack against the fourth amendment of the bill of rights, but it is also an attack against our collective. CISA, and those who have crafted and supported this bill, have become sworn enemies of Anonymous.
"Every action you perform, every word you say, we will know. If you value the sanctity of your loved ones as well as your own [sic], it will be best for you to back down and drop this bill where it belongs - out of our Congress."
Last week saw the US supreme court rule that police need a warrant to search mobile phones seized from suspects, the latest in a series of defeats for US administrations looking to strengthen the powers of police to fight crime through digital means.
Dianne Feinstein, the senate intelligence chair who co-authored the bill, said: "The bill incentivizes the sharing of cyber security threat information between the private sector and the government and among private sector entities.
"It responds to the massive and growing threat to national and economic security from cyber intrusion and attack, and seeks to improve the security of public and private computer networks by increasing awareness of threats and defences."
Sandra Fulton, legislative assistant at the American Civil Liberties Union, criticised the law as an attempt to give the government greater power "to crack down on whistleblowers".
"If misused by this or future administrations, CISA could eliminate due process protections for such investigations, which already favour the prosecution," she said.