Sophos has announced the launch of a new anti-spam service that identifies computers used for malicious or unauthorised purposes.
ZombieAlert has been designed to find PCs that are being controlled from outside an organisation.
They are often used for denial of service attacks and account for about half of all spam, according to Sophos.
Channel sales manager, Zoe Nicholson, said spam had moved beyond the nuisance stage to become a criminal activity. But she said the new service would help organisations track its source.
It works by notifying customers if their Internet Protocol (IP) addresses are listed in public Domain Name Server Blackhole Lists (DNSBL).
This information helped customers locate, disinfect and protect systems from future attacks, Nicholson said.