George Clooney's L.A. home is getting the Fort Knox treatment for his big Obama fundraiser Thursday night. Security's so tight, even the back-up has back-up.

Law enforcement sources tell TMZ, the U.S. Secret Service will be getting help from the LAPD as well the California Highway Patrol to keep POTUS safe at the event.

The LAPD is even planning to bring in its special Counter Terrorist Unit, Jack Bauer style.

But that's not enough for Clooney, who TMZ is told has taken things a step further, hiring a special security team to oversee his own personal safety.

As for specific security measures being taken for the event -- roads will be closed off, bomb-sniffing dogs will be prowling, and plain clothes officers will be on the lookout, TMZ reports.

There's also "air support" -- whatever that means.

As TMZ reported, the party's going to be huge. Wolfgang Puck himself will be catering the $40,000-a-plate affair, and 150 bigwigs are expected to be in attendance.

Bottom line: crash another party.