place this ip range in your ban list >
91.207.4.0-91.207.9.255
and never buy or trade these ip numbers as they have a deep history of spam serving, all related to some entity called steephost, you can whois one the ips if you want more info, theyre address seems to point to a field in a small town in the ukraine. some people in the Ukraine obviously think it useful to spend they’re time spamming websites, problem is these people dont realise that they just encourage large numbers of people to start blocking ukrainian ip ranges in general, which harms the ukraine’s reputation on the internet stage.
It also reduces the number of useable ip numbers in general as those ip’s that have been used for spamming becoming blacklisted, making them worthless from a resale or re-use perspective.
here is some further internet information
further info on honeypotsecurity site
this website is an easy to use way you can also track the rubbish down