USA National Institute of Standards and Technology Akamai Technologies USA National Institute of Standards and Technology Designing an efficient source address validation (SAV) filter requires minimizing false positives (i.e., avoiding blocking legitimate traffic) while maintaining directionality (see RFC8704). This document advances the technology for SAV filter design through a method that makes use of BGP UPDATE messages, Autonomous System Provider Authorization (ASPA), and Route Origin Authorization (ROA). The proposed method's name is abbreviated as BAR-SAV. BAR-SAV can be used by network operators to derive more robust SAV filters and thus improve network resilience. This document updates RFC8704.