Symantec's Internet Security Threat Report found that over 1.65 million new malicious codes were detected in 2008 - up 265 per cent on the 624,267 codes uncovered the year before.
This "explosive growth" means that 60 per cent of all malicious code signatures were created last year, the security specialist said.
Codes that gave fraudsters remote access to confidential information were the biggest threat, accounting for 83 per cent of the total identified by Symantec.
The firm noted that the development of malicious codes is becoming more professional in order to support the underground goods and services that support online fraud.
Many developers of malicious codes are now concentrating on creating variants of existing threats, which can be produced and sold on the underground economy more quickly than entirely new threats, the study found.
Some 68 per cent of the top 50 malicious code samples identified last year were Trojans.