WikiIslam has some automatic features that block potential vandalism automatically. See MediaWiki:Edit Monitor for more information. It also has “pending-changes protection”. If you have spotted vandalism, you can also notify sysops who can block the vandal.
For blocking IP ranges of the format 123.456.X.X, use this as the block text: 123.456.0.0/16 You can also use this IP Block Range Calculator for calculating the range.