Would-be scammers trying for months to use Fish & Richardson to make their classic check-fraud plan work are not succeeding.

As soon as people started contacting the firm last December with questions about Fish & Richardson checks they had received in the mail, the Boston-based firm notified its bank that someone was trying to pass counterfeit checks written on a firm account. Most recently, on Oct. 5, the firm learned from its bank that someone tried unsuccessfully to cash one of the checks, suggesting the scammers may have mailed a new round of letters, says Kelly Largey, chief marketing officer for the 418-lawyer firm.