Google’s Postini division today announced that its e-mail-content-filtering service has been enhanced to detect “logical expressions,” such as credit-card data and Social Security numbers.

Postini says this lets businesses track confidential customer data via e-mail, and the company intends to extend this capability in the future to instant messaging, the Web and Google Apps. 

Adam Swidler, Postini senior product manager, says the e-mail security service includes filtering of more “sophisticated expressions” that extend beyond Postini’s earlier limits to keywords. “This is for compliance and content-policy management, with content-based inspection for inbound and outbound traffic,” he says. “Today it’s for companies using Gmail, but we expect to extend this to instant messaging, the Web and the rest of Google Apps, like Google Spreadsheets.”

Postini isn’t ready to announce a target date, but the long-term goal is to create a feature-rich data-leak prevention service, Swidler says.

The enhanced content-filtering service, available today, lets managers quarantine a message, block it completely or send it on with a carbon copy to an authorized recipient. The service costs $33 per user for one to 250 users. Postini says it is in use at 35,000 businesses.