San Francisco, Feb 18 (IANS): A new email scheme is threatening publishers to unleash bots on their platforms on Google AdSense unless they pay $5,000 in bitcoin.

According to a report in Krebs on Security, the email-based extortion scheme targets website owners serving banner ads through Google's AdSense programme.

"In this scam, the fraudsters demand bitcoin in exchange for a promise not to flood the publisher's ads with so much bot and junk traffic that Google's automated anti-fraud systems suspend the user's AdSense account for suspicious traffic," the report added.

AdSense is a free, simple way to earn money by placing ads on your website.

KrebsOnSecurity heard from a reader who maintains several sites on AdSense that receive a fair amount of traffic.

"Very soon the warning notice from above will appear at the dashboard of your AdSense account undoubtedly! This will happen due to the fact that we're about to flood your site with huge amount of direct bot generated web traffic with 100% bounce ratio and thousands of IP's in rotation - a nightmare for every AdSense publisher," read the message

"More also we'll adjust our sophisticated bots to open, in endless cycle with different time duration, every AdSense banner which runs on your site," it added.

The message demands $5,000 worth of bitcoin to stop the attack.

In a statement, Google said the message appears to be a classic threat of sabotage.

"We hear a lot about the potential for sabotage, it's extremely rare in practice, and we have built some safeguards in place to prevent sabotage from succeeding," said the statement.

Google directed users to go to help centre on its website with tips for AdSense publishers on sabotage.