The number of keyloggers has soared by five-fold in three years and is now the greatest threat cybercriminals have to threaten business networks, according to the latest report by Kaspersky Lab.

The volume of keyloggers jumped by 500 percent between January 2003 and July 2006, according to the Russian anti-virus vendor.

The technique is more difficult to combat than phishing and social engineering methods because keyloggers silently install malicious software on a corporate network, according to the report.

Experts at Kasperksy also warned that hackers have employed rootkit technology to avoid detection, as well as tracking a user’s website use to log keystrokes of particular interest to cybercriminals.