An American cyber-crime initiative may be helping to limit volumes of spam and viruses, according to MessageLabs.

The security firm has reported a 10 per cent fall in the amount of spam it has seen hitting mailboxes in August, and that the proportion of emails carrying viruses dropped about half a per cent during the same month.

Of all email scanned by MessageLabs' anti-spam service, 84.2 per cent was categorised as spam, compared to 94 per cent during July.

The company reported that 6.9 per cent of the emails it scanned were identified as virus-infected during August, a decrease from 7.3 per cent during July.

MessageLabs suggested that, while some of the fall could be attributed to the cyclical nature of spam and viruses, which often drops during the summer months, the US Operation Web Snare initiative could have a bearing.

Web Snare was launched in June by the US Justice Department involving a number of US and foreign law enforcement bodies.

The initiative is targetting significant cyber-crime, such as identity theft, fraud, phishing attacks and computer intrusions, and has resulted in over 105 arrests and 53 convictions to date.

MessageLabs chief technology officer Mark Sunner said in a statement: "The drop in spam volumes may be partly as a result of Operation Web Snare.

"This operation may have removed some of the perpetrators from active service and could have worried others enough to suspend operations for now."

However, Steve Linford, founder of anti-spam organisation Spamhaus, told vnunet.com that there might be a more prosaic explanation.

"We have been joking that it's been hurricane Charlie [as most US spammers are based in Florida]," he said.

"We also think that the Chinese promise of very harsh jail sentences for pornography spammers will have worried those people in China who work with the US spammers."