Ho, ho, ho, it's another White House Christmas brought to us by Osama bin Laden.

In an ultimately vain attempt to keep this Grinch from stealing Christmas, the Bush administration has deployed a new high-tech weapon: the Barney Cam. Americans can log on to the White House Web site and get a hound's-eye-view of where the public used to be allowed, a "virtual tour" of the White House at Christmastime with the first family's Scottish terrier.

Barney is a winsome protagonist, yapping, panting, gnawing, romping -- acting pretty presidential. It's cute the way his scampering toenails go clickety-click on the polished floors. As you study his antics in the rooms where you are no longer welcome, the realization hits:

A dog has taken our place.

First, the back-story:

Because of "security concerns," for the second year in a row most of us can't take an actual tour of the White House to see the holiday decorations.

Generations of Washingtonians and tourists -- regular people -- used to make it a mid-December tradition to see the place decked in green and red and gold. The finest antique Italian creche you ever saw might be displayed in the East Room. The Blue Room would have a towering evergreen wired to the ceiling with ornaments crafted by artists from every state, following some mildly hokey theme thought up by the first lady.

It was Washington's version of making a holiday pilgrimage to Rockefeller Center in New York, or promenading among the Christmas lights on the Boston Common, or attending the Festival of Lights in Niagara Falls -- only more special. You'd feel a little giddy and proud to be treading the same floors where so many powerful people have come and gone to make history for better or worse.

At this time of year you'd notice the White House smelled of pine sap and gingerbread -- which made it seem not so different from your house.

Pat Nixon devised the most beloved part of the tradition in 1969 -- the tours by candlelight open to the public for three nights in late December. This annual ritual was extinguished only last year; between 12,000 and 15,000 people would visit. Counting daytime December tours, an estimated 125,000 would make a trip to the White House part of their holiday season. Year-round, some 1.5 million would visit.

A comparative tally of White House visitors now was not available yesterday, but it's certainly much smaller under the new system: Only school groups through the 12th grade and organized military or veterans groups may tour, as requested through their members of Congress.

(Wait a minute. Isn't John Allen Muhammad, accused in the Washington sniper case, a veteran, just like Timothy McVeigh, the Oklahoma City bomber? Weren't mass murderers Dylan Klebold and Eric Harris students at Columbine High School? Never mind.)

The White House and the Secret Service imposed these restrictions for security reasons -- and, also for security reasons, they won't specify why others must be kept out. "Security reasons" is the new all-purpose explanation for everything.

"We're trying to balance creating a safe and secure environment with allowing access to the White House," says John Gill, a spokesman for the Secret Service.

Earlier this month, a White House spokeswoman told The Post that the president and first lady "are very disappointed that due to security concerns, the White House is not open for public tours this year."

Surely good old American know-how ought to be able to find some way to address security concerns without resorting to the easy solution of just limiting access to the very symbols of what we cherish. Can anybody with power (and therefore access) empathize enough with those out of the loop to understand why that's so important?

Instead we have Barney Cam, unveiled Thursday. Let's take this virtual tour of the White House at Christmastime -- it's all we've got.

Click on to whitehouse.gov. If you happen to be one of the 16 million people in this country with a high-speed Web connection, the video starts playing almost instantly. And if you don't have a fast modem at home, maybe you do at work. (Barney Cam: Threat to American worker productivity?)

Barney's virtual tour is 4 minutes 30 seconds.

See Barney run. See him try to nudge a red Christmas ornament along the floor, running in place on the smooth surface like a cartoon character. Hear the soundtrack of toenails and Christmas carols.

See Barney look out a window on the South Lawn and spy the Washington Monument.

What a fine view the rest of us no longer have.

See Barney check out the tree in the Blue Room, wolfishly appraising a bird ornament.

See Barney enter the State Dining Room and sniff the giant gingerbread White House, a near-perfect replica created by White House pastry chef Roland Mesnier with 80 pounds of gingerbread, 50 pounds of chocolate and 20 pounds of marzipan. Barney seems to be going for a chunk of East Wing.

But you can't really tell, it goes by so fast. You can't get a sense of the massive confection, let alone a sense of the White House itself, which you supposedly own. You feel no giddy pride at being part of something special. That you, of all people, could ever visit the president's house was a great -- and obviously perishable -- feature of American democracy.

See Barney run around in circles on the South Lawn. There's snow on the ground, so the footage must have been shot recently. What a great lawn.

Then Laura Bush opens the door to let Barney back in.

Besides Barney Cam, there are other short videos on the holiday section of the Web site. Laura Bush leads a more conventional tour of the decorations. If you don't have a fast modem but you are online (more than 40 percent of Americans do not have Internet access), you can click onto still pictures of the decorations.

Or you can visit the visitors center a block west of the White House on Pennsylvania Avenue with photographs on display and a video in which Laura Bush says, "Sharing holiday decorations is a longstanding White House tradition."

The public's curtailed experience of the White House Christmas is not exceptional, of course. The experience of much of historic, patriotic, scenic, public Washington is diminished. You can no longer walk at will into the Capitol. You have to join a tour, which has substantially cut the volume of visitors. Even outside the Capitol, you can no longer climb the West Steps to gaze on the Mall, one of the greatest views in the city, no longer freely accessible.

More streets are being closed to cars, following the example of what could be called Timothy McVeigh Way: the stretch of Pennsylvania Avenue in front of the White House that was shut in 1995 after the Oklahoma City bombing. Every time everyday life is altered for a terrorist, it's hard to keep the terrorist out of your mind, which is just what he wanted.

The White House says Barney Cam will be back with new installments.

If current trends continue, maybe we should just nominate Barney Understudy-in-Chief for Americans, visiting all the places regular people are not allowed for security reasons.

Send Barney Cam into those obscure spaces with amazing murals in the basement of the Capitol. Send Barney Cam scampering up and down the West Steps.

The next time NATO or the World Bank hold big meetings in Washington and the police want to erect a 10-foot fence around the center of the city to keep out protesters -- send Barney Cam behind the lines.

When Republicans or Democrats elect a president and make sure only their friends and biggest donors get the best bleacher seats for the inaugural parade -- send Barney Cam on behalf of the rest of us.

Merry Christmas, Osama.

And go, Barney! We're watching.

The Bushes' terrier goes where tourists no longer tread."Security concerns" have reduced the White House holiday tour to a virtual voyage led by the presidential pooch.