In addition, phishing attacks are becoming more sophisticated, with online criminals using a variety of techniques to escape detection in order to gain more time to steal information.
The report notes that home users are the most targeted attack sector, accounting for 86 per cent of all targeted attacks, followed by financial services businesses.
"Attackers see end users as the weakest link in the security chain and are constantly targeting them in an effort to profit," said Arthur Wong, senior vice president of Symantec security response and managed services.
"Given the effect this has on our large and growing customer base, Symantec introduced new metrics to further understand how to better protect customers against these security concerns in years to come."
During the first half of 2006 around 18 per cent of all distinct malicious code samples detected by Symantec had not been seen before, indicating that attackers are more actively attempting to evade detection by antivirus systems.
Furthermore, the number of unique phishing messages detected during that period increased 81 per cent on the previous six months to 157,477.
The report is based on Symantec data collected from more than 40,000 sensors deployed in more than 180 countries.