Anyone found trying to use the tournament's name or brand can be fined up to $150,000 under the Major Events Management Act 2007, and could face legal action if they try to rip off the trademark, said IRB general manager Ross Young.
"It's the malicious corporate ambush where people invest tens of thousands of dollars in intricate campaigns, those are the ones we're after."
He said hundreds of educational letters with cartoons and pictures had been sent out explaining what companies can and can't do.
Each of the 12 stadiums across the country will be protected by a "clean zone" for a period before and after the match.
The Ministry of Economic Development was monitoring each zone, and up to 12 team members would patrol Eden Park around the temporary period, said ministry spokesman James Funnell.
Within each clean zone, any existing advertising was exempt from the law - even if it was for rival brands, he said.
However, many of the key billboard spaces around Auckland had been pre-booked a few years ago by sponsors and the organisers, said Auckland Council licensing manager Carole Todd.
The council is monitoring the wider Auckland area and up to 35 council officers will patrol Auckland every match night, looking for leaflets, freebies, posters, billboards or products that don't have a permit, said Ms Carole Todd.
The officers will also be monitoring noise and liquor licensing.
Council has given out permits for any kind of sale or giveaway on the streets which protect the sponsor's rights, she said.
She said council was looking out for "clever" marketers offering something as simple as a beanie emblazoned with a non-official logo being given out on the way to the stadium, that don't have permits.
"The biggest ambush marketing used to be a streaker with Vodafone across their bottom running across the field when the All Blacks was sponsored by Telecom," said advertising agency TBWA chief executive David Walden.
He said advertisers were now more interested in using publicity to create sales, rather than just pulling a stunt - but he still expected to see a few attempts at publicity stunts.
CRACKDOWN
* Systems are in place to stop unofficial Cup brands getting free publicity
* 12 stadiums across the country will be protected by a 'clean zone' for a period before and after the match
* Anyone found trying to use the tournament's name or brand can be fined up to $150,000