Arlo is software for managing and conducting a Risk-Limiting Audit (RLA). The code for Arlo is open-source and freely available for anyone to use and host. VotingWorks provides a hosted-version of Arlo and customer support when conducting an RLA.
Arlo supports ballot comparison, ballot polling, batch comparison, and hybrid RLAs for single jurisdiction to statewide audits.
RiskLimitingAudits.org describes the history and process of conducting an RLA.