Differences between DQS and Public Mirrors

While from the access technology perspective DQS is not particularly different from the DNSBL service provided by Spamhaus, there are a few important differences between the two one may want to be aware of.

While most of the data are the same, there are a few differences.

  • some SBL listings that are considered more prone to False Positives are not published on DQS

  • DQS records are served over DNS with a minimal 1s TTL (Time to Live) to ensure freshness of the response through caching DNS resolvers, while public mirrors serve data with a 60s TTL

  • DQS data are updated in realtime when new listings appear, unlike the public mirrors, that get only updated at scheduled intervals

  • some datasets are only available on DQS and will never be provided by public mirrors

  • access to public mirrors requires the use of a non-public, non-shared DNS resolver (therefore excluding services like Google Public DNS), while DQS can use any DNS channel

  • access to public mirrors can be inhibited anytime for a number of reasons, usually related with overquerying or observed malicious behavior from the querying network