I signed up for the federal do not call list when it opened in 2004, and for years our landline was blissfully free of telemarketing calls. That’s changed in the past few years as illegal operations, many based overseas, started flagrantly violating the law.

A new free service may give us some peace.

Nomorobo, which launched in September, is like a spam filter for your digital phone line, according to consumer advocate Herb Weisbaum. The service uses the “simultaneous ring” function available on VoIP service to identify robocallers and hang up on them.

The guy who invented it, Aaron Foss, is the software programmer who recently won the top $25,000 prize from the Federal Trade Commission’s Robocall Challenge with this idea. His site promises the service won’t block legitimate robocalls, such as notices from your doctor’s office about upcoming appointments or phone blasts from schools announcing closures. Instead, the service draws from a database of known robocallers culled from state and federal regulators.

The signup was easy and the service began right away. When a call came in from a known robocaller, our phone would ring once or twice and then stop, as the service answered and hung up on them.

Robocallers are constantly switching phone numbers so an occasional call will slip through–which I can then report to the service to add to its database.

Nomorobo isn’t available for all phone lines, sadly. But if you have Internet-based phone service from Comcast, Time Warner, Uverse, FiOs or Vonage or other digital carriers, you can check it out.