McAfee has released the results of its Spammed Persistently All Month campaign.

The project asked a group of 70 users from 10 countries to surf the web unprotected and gather as much spam as possible.

The guinea pigs were able to amass a total of 104,000 spam messages, an average of 2,096 messages per person and 70 messages per day for each user.

Americans topped the spam haul, amassing 23,233 spam messages between five users. Brazil finished a distant second with 15,856 messages, and the UK was fifth with 11,965.

Participants in the study also noticed significant system slowdowns from unwanted software installations.

"In just 30 days there was quite a noticeable change in the performance of their computers," said McAfee Avert Labs senior vice president Jeff Green.

"This showed just how much malware was being installed without their knowledge, and that spam is much more than a nuisance. It is a very real threat. "

The US also led the study in the number of adult-oriented spam messages, while the UK received the highest number of Nigerian '419' messages. Brits received more than 23 per cent of the infamous money transfer scam attempts.

Financial services messages were the most popular spam topics, followed by advertisements and health and medicine messages. Adult emails were the fourth most-popular, while offers for free items were fifth and 419 scams tenth.

McAfee also noted an increasing number of location- and language-specific spam, particularly in France and Germany. The large spam loads in Brazil and Mexico also suggest a new focus on emerging economies.

"Our participants came from all walks of life, from all over the world and, given their interest to take part in the experiment, they were well aware of the problem," said McAfee chief executive Dave DeWalt.

"Despite this, they were all shocked by the sheer amount of spam they attracted in such a short time and the lengths the spammers would go to in order to achieve success."