jno's advice is correct.
Anyone using (say) a PC in a Net Cafe will not be able to be blocked,and even if were to be blocked,it would bar all AB users from that cafe.
More to the point the "tail" of an ISP address changes every time a person logs on.
AN ISP address consists of 3 parts:~
1.The ISP companies own address part,
2. Your area address (for your country & county) part,
3.Your own personal part.
For instance mine would read (as numbers) BT Broadband~UK East Sussex~Then my (changeable) tail number.
Whilst the first 2 parts always stay the same,every time you log on the "tail" changes it's numbers.
This is done by your ISP to block anybody hacking into your PC.
I am a moderator (one of several) at another forum,and this information was given to us by a BY Broadband Technical guy when we were trying to block some abusive posters there.
It might be more usefult yo bring back(as we had on old AB) the green "newbie" names,at least that way when a new name appears it would be obvious what they were?