Hello, i'm lemmymet
I'm studying servers and what plugins they use, also i'm looking at security problems on servers.
And now i use that info to inform you all about how griefers are playing and griefing!
I will give you a tutorial how to protect a server from a griefers perspective
This tutorial will take 30-90 minutes, and are meant for bukkit servers

1. The most used tools under griefers:
A griefer doesnt need much tools, they mostly just have a hacked client or a modpack
Here are the most populair tools:

• Nodus griefing client
  
• Mystic griefing client
  
• Zombe's modpack
  

And here is strong advice:

1. Download the nodus client(use google)
   
2. Login on your server
   
3. Deop yourself
   
4. Ifyou have permissions give yourself the rank every member gets
   
5. Press y and press nuker(under world menu), then press escape
   
6. Hit a block(do it with a iron pick if your are on survival)
   
7. Are you griefing without kick?
   

If yes: You just found a security problem!
If you get kicked: Skip part 2 of the tutorial.

2. Prevent griefing with client mods

1. Download NCP from here
   
2. Copy the jar to your plugins folder
   
3. Reload your server
   
4. You're protected, for the most servers the default config is sufficient to prevent griefing with client mods
   

3. Giving users the possibility to protect their land
Nocheat plus prevents griefing for +-15%, but we want more prevention
And here is one of the best ways, let your users protect their own land!

1. Download this plugin
   
2. Copy the jar to your plugins folder
   
3. Restart your server
   
4. Configure the plugin
   Here are some optimal values:
   A player should have 2500 initial claim blocks, don't give a player too much or too few
   Give him 100-200 claim blocks a hour
   Set the max claim blocks to something like 25000
   
5. Reload the server again
   
6. Profit
   

Inform your users good about the usage and commands for this plugins
Warn/ban people who claim other people's buildings, use /ic then /abandonclaim for that
After this action you prevented 70% of all griefing!

Now it's time to inform you what todo AFTER a grief

Not all griefing can be prevented, so this part is important too!

4. Installing a log plugin
You'll need a mysql database for this, use google if you dont know how you should make a mysql server.
We'll use logblock, this plugin is in developement for a year and is really robust!
Hawkeye was one of the best but the developer disappeared and is gone, it does give problems now for some servers.

1. Download logblock from here
   
2. Copy the jar to your plugins folder
   
3. Restart your server
   
4. Configure the plugin, just edit the mysql connection details
   
5. restart your server
   

If /lb t isn't giving a error you did configure it good!, everything a player does is logged now!
You now can see who destroyed a block and rollback players!

5. Disabling minecraft items/physics
If you dont have essentials download it from here
Enable Essentialsprotect in config.yml and set the items you dont want to happen to true

6. Installing a backup plugin
Well, as a last resort you'll need backups

1. Download minebackup from here
   
2. Copy the jar
   
3. Reload your server
   
4. Configure the plugin to your likings
   
5. If you have worldedit set the snapshot folder in the worldedit config to your backup folder, then you can restore worldedit selections from a backup
   
6. Reload your server again
   
7. Profit!!!
   

7. !For cracked servers! Install a login plugin
You have a cracked server without login plugin?
THEN YOU HAVE A BIG SECUrITY HOLE, the nodus client automatically says when a server is in offline mode, then a griefer will look who's OP!
Griefer logins as OP then do horrible commands(//replace sponge, //removenear 100000 sponge or //sphere stone 99999) that'll destroy the server.
So heres a tuto to prevent this

1. Download authme from here
   
2. Copy the jar to plugins folder
   
3. Reload your server and you're done!
   

If you did it good griefers can't do much on the server :P
Have much luck with your server and here some tips:

• Only give OP to people you know IRL
  
• Dont give plugin.* permissions to members
  
• Dont give OP to people that ask for it(server reviewers)
  
• If you posted ur server on PMC watch it for 2h,there are much griefers here
  
• Make events on your server, people like hunger games, you'll get populairity by events