Netsky was the top virus in July, making it the fifth month in a row that the pesky virus was the number one threat, according to Postini, an email security vendor.

Zafi ranked second last month while the notorious Mydoom.o ranked fifth, Postini said.

Earlier this week, antivirus vendor Sophos released a virus chart for July that showed Zafi as the most prevalent threat.

Postini also said that spam accounted for about 75 percent of all the email it processed in July, down from 76 percent in June.