User blog comment:Meighan/Wiki Wisdom: Reacting to Trolls and Vandalism/@comment-3441771-20111116082728/@comment-2200849-20111124181017

Unfortunately, most IPs are dynamic and change over the passage of time, ranging from a few days to a year. The problem is more significant if said anon is editing through an Internet anonymity network such as Tor; generally, such users, known as exit nodes are blocked if they are not caught by Wikia's anti-Tor extension.