IT contractors have been urged to scan any of their removable devices for security threats by a major software vendor.

The most prevalent threat is currently Trojan.AutorunInf.Gen, a generic mechanism designed to spread through USB devices, according to the latest report from BitDefender.

This particular threat currently accounts for 13 per cent of all global malware infections, BitDefender claims.

Any infected devices can pass the malware between networks, which could be of particular concern to IT contractors working for more than one company.

Next most prevalent is the "infamous" Kido, or Conficker, a worm that exploits a common windows vulnerability, which can be easily eradicated by updating the operating system.

Dan Glassner, vice president of enterprise marketing at Trend Micro, told information security website Datamation that malware is the biggest threat facing IT.

BitDefender will offer professional advice to IT contractors concerned about malware at industry event Infosecurity Europe 2010, held at London's Earls Court from April 27th - 29th.