If the Homeland Security Act is not amended before passage, here is what will happen to you:

Every purchase you make with a credit card, every magazine subscription you buy and medical prescription you fill, every Web site you visit and e-mail you send or receive, every academic grade you receive, every bank deposit you make, every trip you book and every event you attend -- all these transactions and communications will go into what the Defense Department describes as ''a virtual, centralized grand database.''

To this computerized dossier on your private life from commercial sources, add every piece of information that government has about you -- passport application, driver's license and bridge toll records, judicial and divorce records, complaints from nosy neighbors to the F.B.I., your lifetime paper trail plus the latest hidden camera surveillance -- and you have the supersnoop's dream: a ''Total Information Awareness'' about every U.S. citizen.

This is not some far-out Orwellian scenario. It is what will happen to your personal freedom in the next few weeks if John Poindexter gets the unprecedented power he seeks.

Remember Poindexter? Brilliant man, first in his class at the Naval Academy, later earned a doctorate in physics, rose to national security adviser under President Ronald Reagan. He had this brilliant idea of secretly selling missiles to Iran to pay ransom for hostages, and with the illicit proceeds to illegally support contras in Nicaragua.

A jury convicted Poindexter in 1990 on five felony counts of misleading Congress and making false statements, but an appeals court overturned the verdict because Congress had given him immunity for his testimony. He famously asserted, ''The buck stops here,'' arguing that the White House staff, and not the president, was responsible for fateful decisions that might prove embarrassing.

This ring-knocking master of deceit is back again with a plan even more scandalous than Iran-contra. He heads the ''Information Awareness Office'' in the otherwise excellent Defense Advanced Research Projects Agency, which spawned the Internet and stealth aircraft technology. Poindexter is now realizing his 20-year dream: getting the ''data-mining'' power to snoop on every public and private act of every American.

Even the hastily passed U.S.A. Patriot Act, which widened the scope of the Foreign Intelligence Surveillance Act and weakened 15 privacy laws, raised requirements for the government to report secret eavesdropping to Congress and the courts. But Poindexter's assault on individual privacy rides roughshod over such oversight.

He is determined to break down the wall between commercial snooping and secret government intrusion. The disgraced admiral dismisses such necessary differentiation as bureaucratic ''stovepiping.'' And he has been given a $200 million budget to create computer dossiers on 300 million Americans.

When George W. Bush was running for president, he stood foursquare in defense of each person's medical, financial and communications privacy. But Poindexter, whose contempt for the restraints of oversight drew the Reagan administration into its most serious blunder, is still operating on the presumption that on such a sweeping theft of privacy rights, the buck ends with him and not with the president.

This time, however, he has been seizing power in the open. In the past week John Markoff of The Times, followed by Robert O'Harrow of The Washington Post, have revealed the extent of Poindexter's operation, but editorialists have not grasped its undermining of the Freedom of Information Act.

Political awareness can overcome ''Total Information Awareness,'' the combined force of commercial and government snooping. In a similar overreach, Attorney General Ashcroft tried his Terrorism Information and Prevention System (TIPS), but public outrage at the use of gossips and postal workers as snoops caused the House to shoot it down. The Senate should now do the same to this other exploitation of fear.

The Latin motto over Poindexter"s new Pentagon office reads ''Scientia Est Potentia'' -- ''knowledge is power.'' Exactly: the government's infinite knowledge about you is its power over you. ''We're just as concerned as the next person with protecting privacy,'' this brilliant mind blandly assured The Post. A jury found he spoke falsely before.