In its 2010 security report released Tuesday, Symantec Corp.  said that the annual average global spam rate was 89.1 percent, an increase of 1.4 percent over the preceding year, the San Jose Business Journal reported.

Symantec also reported that in August, the global spam rate peaked at 92.2 percent when the proportion of spam sent from botnets — networks of thousands of compromised computers, or bots —  rose to 95 percent as a new variant of botnet was put into use. For most of 2010, spam from botnets accounted for 88.2 percent of all spam, according to the report.

“It is predicted that in 2011 botnet controllers will resort to employing steganography techniques to control their computers. This means hiding their commands in plain view — perhaps within images or music files distributed through file sharing or social networking websites. This approach will allow criminals to surreptitiously issue instructions to their botnets without relying on an (Internet service provider) to host their infrastructure, thus minimizing the chances of discovery,” the report said.

Symantec said that in the past year more than 339,600 malware strains were identified in malicious e-mails blocked, representing more than a 100-fold increase since 2009.