Clean up your SPAM IP addresses. DocDownload has been having trouble with serious hits from SPAM IP addresses from across the world, mainly (it appears) from Russia, but of course not too easy to conclude. If you try to get a handle on it, it will probably increase dramatically, which could suggest one of the reasons for SPAM is anti-SPAM service providers, though again, not that easy to conclude. So, lots of time wasted, and making the problem worse, not better.
docDownload has done its research & has decided to go with https://cleantalk.org
For a number of reasons. Take a look. Worth a try.
A picture of a page in CleanTalk's Anti-SPAM log.