Reactive Spam Filtering Works!
With regards to our previous post last month Where Does All The Spam Come From we briefly mentioned that our own custom built, reactive real time blackholing service was in place.
This means that should a particular IP send us more than 5 emails, which the spam filter tags as spam, it will be blackholed for up to 1 week. We discovered that a significant amount of spam is sent from compromised hosts / servers. Rather than have our systems process spam from these hosts repeatedly, reactively blocking them after a certain amount of spam had come into the network was a logical choice. Reduce the risk of any of that spam actually getting through to our customer base, and reducing the CPU load on the spam processing servers.
We’ve noticed that over the few months we have been monitoring this, the amount of email being filtered by the spam servers has reduced whilst maintaining the proportion of total email received. July | August | September.