Late last week, the House passed the Cyber Intelligence Sharing and Protection Act (CISPA), despite a veto threat from President Obama. Privacy advocates and the media were especially alarmed by last-minute amendments, leading to "dramatic headlines like 'Insanity: CISPA just got way worse..' and 'CISPA is ridiculously hideous,'" says Jeff John Roberts at GigaOm. Earlier this year, the same kind of alarm bells, plus a heavy dose of "internet muscle" from big technology companies, were enough to derail another piece of proposed internet regulation, the Stop Online Piracy Act (SOPA). But this time, "these same [tech] companies have been quiet as church mice," or even supportive of CISPA. What gives? Here's what you should know:

Briefly, what is CISPA?

Presented as a bill to help the government and private companies collaborate to stop cyber-attacks, CISPA is so vaguely worded that critics have dubbed it "Big Brother" legislation that would give the government and military agencies carte blanche to root through your email and other online data repositories. The law would sunset after five years unless Congress reauthorized it.

What amendments have people worried?

Among the most worrisome is an "odious" amendment from Rep. Ben Quayle (R-Ariz.) that would broaden the scope of what can trigger government surveillance, from the already nebulous "threats" to "cyber security" and "national security" to the need to protect individuals and, specifically, children, say Mat Honan and Brian Barrett at Gizmodo. In other words, "any suspicion of anything illegal on the internet — not just the vague Chinese cyber warfare threats the bill had built its stature on — is enough for the government to go through your entire online life."

Which companies support CISPA?

Defense contractors, telecoms, and power utilities all sent letters of support, as did Facebook, Intel, Microsoft, IBM, and Oracle. Tech trade groups are on board, too, says Hayley Tsukayama at The Washington Post. In other words, "the technology industry is fully behind the bill."

Why are tech giants backing CISPA?

At least three reasons, says GigaOm's Roberts. First, this isn't SOPA, which would have deputized the tech companies as "copyright cops." Under CISPA, they can pass customer data to the government if they choose, or not. Second, the bill is going nowhere fast — Obama has promised to veto it — so why "kick up dust" now? And lastly, cyber attacks are a real and growing problem for tech firms, and they want "new tools to help them fight back."

What happens next?

The battle moves to the Senate. "Expect the resistance to grow," says WebProNews' Zach Walton. "The internet wants CISPA to die," and "any kind of internet regulation will always be seen as an attack on those who live and breathe the internet."

Sources: GigaOm (2), Gizmodo, House Intelligence Committee, PC World, Washington Post, WebProNews