The federal judiciary and several state courts are warning the public of an email scam in which emails—supposedly from the courts or law firms—include false information on nonexistent cases and, in some instances, carry viruses.

Federal judiciary officials noticed an uptick in complaints about problematic emails this month, according to a spokesman. Officials are advising recipients not to open any attachments or links until they check with whichever court is listed. Courts typically do not send emails unless parties agree to receive documents in a certain case electronically.