Comcast is expanding its free Constant Guard anti-botnet service for Xfinity customers to include anti-malware, secure backup and identity fraud protection.

The Internet service provider launched a trial of Comcast Guard in 2009 and took it nationwide last September, alerting customers when their computers appear to have been compromised by malware.

On Thursday, the company will be adding Norton Security Suite, Secure Backup & Share and Identity Guard from Intersections Inc. to its enhanced Constant Guard service. The services are free with an Xfinity Internet service subscription.

Customers can pay more for additional identity fraud protection services such as proactive monitoring, alerts of personal information such as Social Security numbers, and access to full credit profiles and scores.