US 12,309,204 B2
SPF layering for performant message authorization assertions
Keith Wayne Coleman, Atlanta, GA (US); and Richard Duncan, Atlanta, GA (US)
Assigned to Fraudmarc Inc., Atlanta, GA (US)
Filed by Fraudmarc Inc., Atlanta, GA (US)
Filed on Oct. 14, 2022, as Appl. No. 17/966,719.
Claims priority of provisional application 63/255,484, filed on Oct. 14, 2021.
Prior Publication US 2023/0121553 A1, Apr. 20, 2023
Int. Cl. H04L 9/40 (2022.01); H04L 51/212 (2022.01)
CPC H04L 63/20 (2013.01) [H04L 51/212 (2022.05)] 17 Claims
OG exemplary drawing
 
1. A method comprising:
generating a Sender Policy Framework (SPF) policy; wherein the SPF policy comprises:
a top layer SPF policy comprising a plurality of terms, each term of the plurality of terms corresponding to a category of a plurality of categories, and
a plurality of second layer SPF policies, each second layer SPF policy corresponding to a particular category, of the plurality of categories, wherein each second layer SPF policy indicates a set of IP addresses in the particular category; and
applying the generated SPF policy to an IP address of a source of a received email message to determine a qualifier associated with the received email message;
wherein each term, of the plurality of terms, comprises:
an SPF mechanism;
an SPF qualifier; and
a reference to a particular one of the plurality of second layer SPF policies; and
wherein the plurality of second layer SPF policies includes a default second layer policy, and wherein the set of IP addresses indicated by the default second layer policy corresponds to one of the following:
a set of all IP addresses, or
an inverse of a union of IP addresses indicated in all other second layer SPF policies.