Code Green Networks is introducing an appliance that can help customers protect trade secrets and meet regulations that govern the way corporations protect sensitive data.

The company's CI 1500 device searches emails before they are sent to offsite destinations to determine whether they contain sensitive information that should to be confined to company facilities. If so, the machine blocks the traffic and can alert users and IT security about infractions.

The appliance, which plugs into a network switch, works by hashing the data to create unique representations or fingerprints of files and segments of data content within files that have been designated sensitive. As emails are sent, the device performs a similar hashing of all outgoing content and compares it with the hashes of the data that it is supposed to block. If fingerprints match, the email can be quarantined, blocked or re-routed via SMTP commands.

The CI appliance scans at the application layer so it can view content of files. It is deployed on the large area network (LAN) side of firewalls to screen traffic before it gets on the internet, and can scan half a million emails per hour, the company said. To create the fingerprints, customers give the CI 1500 rights to log on to servers containing the sensitive data, and the machine automatically hashes it.

With the appliance, users can set detailed policies on blocking data. For instance, if certain sensitive information is to be made public on a certain date, the device can block emails containing that content until that date, but allow them afterwards.

In addition to blocking sensitive emails, the device can compare bodies of data to find related information. It could, for example, compare student papers to a body of known works to detect plagiarism. It could also be used to compare source code for programs as a way to detect software copyrights, the company says.

The company competes against the PortAuthority, Tablus and Reconnex, said Charlotte Dunlap, an analyst with US-based Current Analysis. Code Green is different in that it has designed appliances specifically for small to midsize businesses, she said, where others aim at larger customers and offer products that can cost four times as much.

CI 1500 costs $25,000 (£16,800) with a 250-user licence, $50,000 for a 1,000-user licence and $100,000 for unlimited users.