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In January, America’s major tech companies joined everyday internet users to break the back of a reviled law called SOPA. Months later, Washington is brewing a new law that alarms many SOPA opponents — but this time the same companies have been quiet as church mice.

On Thursday, the US House of Representatives passed the Cyber Intelligence Sharing and Protection Act, a law that will make it easier for companies to share data with the government. On its face, the law known as CISPA has a laudable purpose — to help companies and the government prevent and respond to attacks on the nation’s computers. But civil libertarians warn that the current version of the law will result in a raft of new Patriot Act like rules that will diminish our privacy rights even further.

The vote has already produced dramatic headlines like “Insanity: CISPA Just Got Way Worse..” and “CISPA is ridiculously hideous.” So the press and privacy groups have raised the alarm — but where are the tech companies whose internet muscle smashed SOPA?

We put in calls about the vote to some of our Silicon Valley sources and the response has been nothing but crickets. Silence from Google. Ditto from Facebook. Ditto from Apple (although tight-lipped Apple would probably respond with a “no comment” to news of a meteor hitting Cupertino).

So what gives? Why are these companies ducking the fight? Well, for starters, the two laws are very different: among other things, SOPA would have turned them into copyright cops, while CISPA simply gives them the option to pass on data if they choose.

Secondly, cyber-attacks are serious stuff for such companies. For just one example, read Stephen Levy’s In the Plex description of how the Chinese government broke into Google’s computers and stole not only code, but the Gmail messages of political dissidents. China is plundering US tech secrets on a regular basis and it’s understandable that the firms would welcome new tools to help them fight back.

Whether CISPA is the right tool is another question, of course. But the point, for now, is that CISPA doesn’t harm the self-interest of Silicon Valley companies so they have little incentive to kick up dust. (Facebook offered initial support for the goals of the bill but has since gone silent).

Finally, CISPA is not going anywhere fast. It passed the House with Republican support but is unlikely to make quick headway in a Democrat-controlled Senate, especially after the Obama administration threatened to veto it. This means the tech companies may be simply keeping their powder dry, betting that no law is going to pass until after the November election. Or maybe they just don’t care.

Either way, CISPA opponents looking for their SOPA allies to ride to the escape may have a long wait.

You can learn more about CISPA from our FAQ, Mathew Ingram’s comparison of CISPA and SOPA or our “step-by-step guide to making CISPA suck less.”