Half of Asia's e-mail messages sent in the second half last year contained spam despite advances in preventive software.

The world's largest software company Symantec on Monday said the figure was lower than the 61 percent in the first half last year, but showed that advances in anti-spam software have a long way to go.

By region, 56 percent of spam sent worldwide came from the United States, 12 percent from China, nine percent from South Korea and seven percent from Canada.

The majority of spam advertised health services, followed by products and financial services.