WWW- An Internet rogue apparently hacked into T-Mobile’s heavily used Web site to access Paris Hilton’s cellphone data, enabling the thief to splash the heiress’s racy phone snaps, celebrity numbers and notes-to-self across cyberspace, experts said yesterday.

The ‘Net stealer likely logged on to the site and either garnered Hilton’s password or bypassed that security feature altogether to gain access to data from her Sidekick II personal digital-assistance device, they said.

“I think the hacker just decided to pick her as a test case,” said Kevin Poulsen, news editor of SecurityFocus, an online site specializing in computer security and technology.

Hilton was already among a handful of celebrities suspected of having had their T-Mobile accounts hacked into by 22-year-old computer whiz Nick Jacobsen last year.

Jacobsen, who is not a suspect in the current hackings, “cracked the database that stored passwords and got those he was interested in and logged on. The very same thing could have happened here,” Poulsen said.

T-Mobile was scarce with details on Hilton’s case yesterday, but said it was investigating.

The company is not discounting “the possibility that someone had access to one of Ms. Hilton’s devices and/or knew her account password,” said spokesman Bryan Zidar in a statement.

As a result of the hacking, the contents of Hilton’s Sidekick II have been speeding around cyberspace, proving that just because you gave your pal your private number, it doesn’t mean it’s safe.

The cyber attack has forced a slew of celebrities to field hundreds of prank calls and change their numbers.

More than 500 big-name acquaintances, including Luke Wilson, Adrien Brody, Eminem and tennis stars Andy Roddick and Mark Philippoussis – not to mention recently separated San Francisco Mayor Gavin Newsom – had their numbers and e-mails posted on Web sites.

Justin Timberlake, Ben Affleck, Russell Simmons and Carson Daly also found themselves referenced in the heiress’ notes-to-self on her $200 handheld gizmo – transcripts of which were apparently ripped straight from the Web pages of Hilton’s online T-Mobile account.

Hilton’s rep said the heiress has changed her number and is still reeling from the debacle.

She had even promoted the Sidekick II in TV ads.

“We’re just trying to find out how this all happened. I have no idea what is going on or if the FBI is investigating,” said her publicist, Gina Hoffman, who added that the heirhead is in Florida filming a new season of the “The Simple Life.”

The FBI would not comment on whether it has launched a probe.

A slew of Web sites posted what appeared to be her topless pictures, as well as saucy texts and months of notes-to-self that she had typed into her Sidekick.

Web sites now show a gallery of digital pictures seemingly snapped by the heiress – many of which include her apparently half-dressed and saucily sucking face with a girl.

Lucky recipient “Mark 7” – could it be Mark Philippoussis? – received, “I miss you and want you” paired with apparent pics of Paris in a lesbian lip clinch and a message titled “Happy Birthday” on Nov. 4.

On Nov. 7, the same recipient received messages titled, “My Ass” and “Hello Sexy,” paired with what appear to be naked pictures of the heiress.

Hilton’s personal jottings meanwhile include: “Get birth control kill pill” and “Call maroon 5,” in a shopping list of notes the heiress made to herself over a four-month period from September to mid-February.

In a note apparently to British supermodel Naomi Campbell on Oct 8, she wrote, “You wanna leave soon, I’ll pretend I have 2 go pee and u wait 3 mins then come by yourself to the back entrance.”

In another note on Sept. 29 Hilton rants: “And what conversation might that be, bitch? What do you think, Kristen. Did she learn her lesson?” It’s not clear who she was referring to.

Among the boldface names suffering from sudden exposure:

* Lindsay Lohan, Paris’ gal pal about town in L.A., was deluged with calls from all over the world, especially from Japan where her flick “Mean Girls” recently premiered, her flack said.

* “The Insider’s” Pat O’Brien said he received hundreds of text messages on his cellphone from callers across the globe, including one message, which read, “Hello, I am from Israel. Can I have $100?”

* Paris’s party pal Ashley Olsen had more than 100 calls logged on her phone by early Sunday, a friend said.

The Olsen twin called Paris to ask what was going on. The heiress “said she would come over [to visit Olsen and explain], but Paris never did,” the pal said.

* Deejay Samantha Ronsen had cybersurfers snickering after a prankster posted a recording of a call he made to her cell phone in which he said he didn’t like the music on her Web site. The furious female spinner fumed, “How did you get my number, dude?” to which the prankster gleefully replied, “Paris gave it to me.”

* Former Paris squeeze Nick Carter was recorded by the same caller who apparently dialed up the Backstreet Boy pretending to be a T-Mobile technician warning him his details had been posted on the ‘Net.

The joker explained to a confused Carter he could now look up his personal details on “GFY.com.”

* “Entourage” star Kevin Connelly said he had received between 200 and 300 prank calls Sunday.

* New York nightclub queen Amy Sacco complained her phone was “ringing every 10 seconds” from all area codes across the United States. She had changed her number by yesterday morning. By yesterday, almost all the private numbers from Paris’ contacts list posted on the ‘Net were disconnected.

Eminem’s phone number had been changed. Anna Kournikova’s number was busy. Limp Bizkit frontman Fred Durst’s voice mailbox was full.

B-list action hero Vin Diesel, Cher’s son, Elijah Blue Allman, socialite Bijou Phillips and hip-hopster Pharrell Williams also changed their numbers.

Fans and pranksters rushed to snatch the ditched celebrity numbers, one Web site reported.