While many working Americans are heading into the office and starting their day, spammers are busy, too, readying for their next onslaught of junk messages. According to a new report from Symantec, spammers favor the same work schedule as the typical American office worker.

The research, conducted by Symantec's MessageLabs, indicates that spammers are most active during the US working day for a variety of reasons, but could be because most are either based in the US, or find the workday a good time for potential success, said Paul Wood, MessageLabs Intelligence senior analyst.

"Like any direct-marketing agency, they have direct times when they will want to send their mail shots," said Wood. "It's usually in the mornings, when people are more receptive and have not yet gotten into their work cycle, before the inbox fills up."

If you are located in the US, spam activity peaks at between 9 10 a.m. local time, and trails off to much lower levels overnight, according to the research. The report also said Europeans are likely to receive a steady stream of spam throughout their day, while users in the Asia-Pacific region are likely to start their day with an inbox already full of spam, with only small amounts trickling in after this point until the evening.

The incidence of spam on corporate networks has increased around 5 percent compared to last month's MessageLabs analysis. Spam accounts for more than 90 percent of all email messages, according to the report. One in 317.8 emails in May contained malware and one in 404.7 emails comprised a phishing attack. More time spent on web mail and social networks is aiding in the increase, according to the report.