Facebook says it is backing a new cyber-security bill due before US Congress later this month.
The HR 3523 Act would enable the government to access web users' private data on suspicion of a cyber threat.
The act, dubbed the Cyber Intelligence Sharing and Protection Act (Cispa), would also allow easier information-sharing between security agencies and private web firms.
Advocacy groups claim that it is aimed at file sharers rather than hackers.
First introduced on 30 November last year, the proposed law - which is due before Congress on 23 April - has been criticised by advocates of internet privacy and neutrality.
Facebook, AT&T, Intel, Verizon, and Microsoft are among some 800 firms who have reacted positively to the bill.
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