BitNinja has a challenge list, a block list, and a allow list. All three have an account level and a global level.
The account-level challenge listing, block listing or allow listing only takes effect on the servers under the account.
If an IP address gets challenge listed due to an incident or manual listing ( account level ), after a certain amount of incidents, this IP will be globally challenge listed.
If there are even more incidents generated by the IP address the Address will be globally block listed
IP addresses challenge listed on the account level or globally can be delisted via CAPTCHA. This can be done by sending an email address to a mail server where the Ip is challenge listed or by accessing one of the domains where the IP is challenge listed and solving the CAPTCHA.
A block listed IP address can not be delisted via the CAPTCHA.
If an IP address gets challenge listed at BitNinja, we keep logging the requests from the IP address until it is not delisted from the challenge list. This means the reason why the IP address got challenge listed is not even close to the recent incident logs.
You can read more about the IP filter module and the CAPTCHA module.