For every 4,756 business e-mails sent from March to August, just one contained an offending or nonwork-related attachment, such as pornography, cartoons, jokes and greeting cards. That's compared with a 1,357-1 ratio in the same period last year, according to a study from e-mail security firm MessageLabs.
The company could not say for certain what caused the drop but speculated that stricter enforcement of corporate policies could be helping.
MessageLabs also noted a fall in spam and viruses in circulation in August. Of all messages scanned by the company that month, 84.2 percent were spam, compared with 94.5 percent in July. About 6.9 percent of e-mails were found infected with a virus during August, compared with 7.3 percent the previous month.
"The summer months are often a quiet time for virus and spam distribution--despite exceptions like last August's SoBig.F virus. Virus activity tends to be cyclical, with periods of stability punctuated by outbreaks of varying significance," Mark Sunner, chief technology officer of MessageLabs, said in a statement.
"The drop in spam volumes may also be partly as a result of the United States' Operation Web Snare, during which more than 150 people were arrested for a variety of online criminal activities, including spamming," Sunner said.
Unsolicited material sent over e-mail has emerged as a major problem for businesses and home Internet users. According to researcher IDC, spam accounted for 38 percent of the 31 billion e-mails sent each day in North America in 2004.