WHAT TO DO WHEN they COME!!

Quick Definitions
Here's a brief definition of each: There are much more thorough definitions, but those will be sufficient for this page. Most of the information here will be about vandals and trolls, and not spammers so much.
 * Vandal: wants to harm the wiki.
 * Troll: wants to provoke you and get you upset.
 * Spammer: ca n be someone who wants to sell you something or someone who posts the same kinds of things over and over again.

Reasons Why People Vandalize
At first glance, it's tempting to ask, "Why would anyone want to hurt this place?" It's very much like asking why anyone would steal, hurt someone, lie, or any of the other questions that you might ask when someone does something wrong.

But, it doesn't really do any good to ask the vandal/troll those kinds of questions. You probably will not get an answer, and sometimes simply asking the question gives the vandal/troll what they want.

Here are some of the reasons vandals and trolls do what they do:
 * They are looking for attention.
 * It's fun for them.
 * They want an ego boost.
 * They enjoy making people upset.
 * They want to shock people.
 * It gives them a feeling of power or being in control.
 * They want revenge or to punish others for something that happened on the wiki. This can be for something as small as you undid an edit they made. ("If I can't do what I want, I'll make sure no one else can use the wiki, either.")
 * They would rather destroy something than work to build it.

Returning Vandals/Trolls
There will always be people that want to cause problems, and that is their only reason for visiting a wiki. Being blocked doesn't always deter them.

A lot of times it's obvious that they are the same users because the IP addresses or account names will be similar. Other vandals and trolls make more of an effort to hide what they are doing. IP addresses and user names will not have anything in common.

In either case, there is something in common: the edits they make. It is very hard for people to completely change their behavior and manners, so the more they vandalize and post troll comments, the easier it becomes to see patterns in their edits. Some of the patterns are immediately apparent, such as names or phrases they repeatedly use. Other patterns take a little longer to figure out.

It can be annoying when these kinds of people keep coming back, but there are a few ways of handling them. First, having a team of people that review all the edits being made (and have the ability to fix them). They can also be helped out by people like you who also spot problems and use the undo button to change the edit back.

Second, we can contact Wikia when a person keeps being a problem. They can check their system and take action globally across many wikis, such as reports of all edits made by an IP address or account, then issue a block or disable the account if it's warranted. This happens in extreme cases.

How You Should React
The simplest answer is don't react.

When you get upset by what they do, they win. Fixing problems should never be a competition, but for some vandals and trolls, it actually is a game to them to cause problems.

The best way to handle the problems is to deal with it in a impartial or matter-of-fact manner. Leave your personal feelings and personal comments out of the situation. This can be hard to do, especially if you're on the receiving end of an attack, but the less you give them in the way of a reaction, the less they get out of it.

Additionally, if you make a big deal out of what is happening, such as leaving personal comments in the summary, other people may get curious about what is going on and fall into the trap of reacting to the vandalism/troll comments.

For some, if they don't see that they're getting much of a reaction to what they're doing, they don't get any satisfaction out of it, they get bored, or it stops being fun for them. In these cases, they may give up what they're doing or will go to some other wiki to see if they can get a new audience there.

Steps To Take
Steps you should take when fixing vandalism or trollish edits: An easy way to think of this is "If I was talking to them in person, would I be talking coolly and calmly? Or would I be panicking, getting angry, getting frustated?" If you're not calm and collected, you're letting the vandal or troll get to you. Take a step back, wait a bit and realize that's what a lot of them want. Then take another look to see if there's a more objective way of dealing with them.
 * Don't react. Be objective/matter-of-fact.
 * Reference policies when appropriate.
 * Save yourself the trouble. Don't bother with "Why are you doing this?" messages.
 * Some wouldn't bother reading the message anyway.
 * Vandals and trolls want this reaction.
 * A lot of spam is automated, so no person would be around to read the message.
 * Leave a message for an admin if you need some assistance cleaning things up, such as deleting pages or alerting them to a user that should be blocked.
 * Don't leave Chicken Little messages ("The vandal is back and they're going to ruin the wiki," etc.)

Actually Talking to the Vandal/Troll
In general, only leave official notices on their Talk page, in the same manner listed in the "Steps to take" section above. Trying to help them understand what they did was wrong oftentimes backfire because it shows them you are reacting to what they did. Remember, vandals and trolls want attention and will take whatever you give them in any form you give them, so the less you interact with them, the better.

Impact of Vandalism/Edits by Trolls
The way a wiki is set up, there is basically nothing that can't be fixed. We can undo edits, we can go back to an earlier version of the page, we can delete and undelete pages, and we can delete and undelete files. If there happens to be something an administrator on the wiki can't fix, we can ask for help from Wikia. Their staff members can dig deeper into the workings of a wiki and fix/prevent problems more thoroughly.

So what it comes down to is, no matter what the problem is, it's only going to be a problem for a short while. Sometimes it's spotted immediately and other times it's a few hours — it just depends on how busy the wiki is, and when the next time an admin logs in.

The problem may not be pleasant or nice to look at until it is fixed, but it will be fixed. While it's being fixed, don't panic and don't react to what is going on.

Resources

 * Blocking
 * Vandalism and Spam Task Force
 * Reverting
 * Contacting Wikia