Specific IP addresses not being blocked in Blacklist Manager

I can see through Google Analytics several sites that are attacking my site. I’ve pinged those URLS (there’s no information for them under WhoIs) to discover their IP addresses. I’ve entered those IP addresses under the Blacklist Manager in all-in-one. Most of those sites are now blocked, but there are two that are still accessing my site. Can you explain to me what Blacklist Manager is doing? And secondly is there some way to block these malicious IP addresses?
Thanks for your help with this.

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