Tutorials/Griefing prevention

Griefing is the act of ruining other people's creations on a multiplayer Creative or Survival server. It is frowned upon by the majority of Minecraft users because it ruins many hours of work and makes maps untidy. Some players just consider griefing as another way of playing the game. In best case scenarios, the griefer is quickly removed from the server and their damage is trivial to repair. At worst, griefing can destroy an entire server if it does not have backups available.

The most effective way to fight griefers is to have the Admin or an Op regularly monitor players by using the teleport Op command. If a griefer is found, a /kick or /ban command is usually used. Sometimes, a griefer can change their name to evade the ban. If this occurs, an IP ban can be used on the perpetrator's IP address, but griefers can sometimes get past this ban as well by using a proxy to change their IP. When this is the case, it is probably best to create a whitelist for all trusted players or to shut down the server until the griefer gets bored and moves on. A common way to keep griefers from entering a server while no Ops are online is to use Spawn Jails. If built properly, they will ensure no player will be able to enter the map unless an Op lets them. However, some players consider this a rude practice.

Another method is to require emails to be sent to the admin to be able to build. This way, impatient griefers and those who do not read the rules will not be able to edit the map.

Server Turning
Some griefers decided that a server might be too hard to destroy, as it is too well protected, so he/she might decide to use social engineering and get some of the server staff on their side. Then when they have a good amount of people on their side they go to the owner and force him to agree. This is done by making promises or agreeing with what they think is a problem with the server. When the player does this, every person's thought counts. Even the players. This is rarely used by griefers, but is becoming more common each day. A major example of this is "United Craft". The griefer turned the co-owner and half of the staff on his side, when he finished, the server ended. Because the co-owner and staff went on his side, they managed to get the server's AOL and held the youtube hostage. The griefer converted the owner and staff (and co-owner) into griefers. The best way to make sure this doesn't happen, is to listen to your players and staff, make sure you don't fall for the griefers tricks, and don't listen to their siren call. They will manage to break you, over time. You know which ones these griefers are, because they will talk. Unlike the usual griefer who comes in and keeps to himself, these griefers are more public and talk.

Random Destruction
Random destruction is when a griefer destroys random blocks, putting holes in walls and other structures, making them look broken and messy. Griefers may also target a single structure, working to destroy it completely. If no Ops are present, one way to combat this type of destruction is to repair the damage by hand until the griefer gets bored and leaves. You can also try digging griefers into holes and seal them. Sometimes griefers will use the "Hit & Run" technique. For instance, a griefer will destroy blocks in something and then go away.

Random Construction
The opposite of random destruction, random construction occurs when a griefer creates random blocks on constructions or anything else on a map, making it look messy. Sometimes they fill up other structures with material like cobblestone. The way to combat this is to remove the extra blocks. Again, continue this until the griefer gets bored and leaves. This type of griefing may not seem as bad as the first, but it can be just as annoying to builders, and as fun to the griefers. Often griefers both destroy and create blocks in their quest to gain enjoyment at the expense of others. Another type of random construction is adding to people's structures and claiming that they're "just making it better."

Treeing
Treeing is when a griefer rapidly plants trees in someone's house. This can be very effective in most servers because, depending what mod or save system you use, trees cannot be rolled back. It isn't that much of a problem, as trees can be destroyed quite quickly.

Splashing
Since the 1.0 introduction of potion brewing, a griefer can lure a player(s) using promises of valuable objects, such as diamonds and other rare items, if the victim goes to the griefer's location, but instead of getting the promised goods the griefer throws damaging splash potions at the victim, possibly killing him and losing his items in the process. If the potion fails to kill him (due to poor aim and/or the victim is wearing armor) usually the griefer will attack him until he dies, still looting his items. Cautious players can prevent this with milk, seeing as it cancels out all potion effects, and armor, in case the griefer attacks him.

Tree/Sapling Removing
This is the opposite of tree spamming; griefers prevent people from getting the precious wood on a server. In a large region, griefers can remove trees, and steal all saplings around, from chests using their X-Ray mods. For "security" griefers can throw their stolen stuff in lava or jump in the void. Whether this is considered griefing or not depends on the server, but it can be hindering for newcomers to the server that need wood to get started. Some servers have the kit plugin so tree removers won't be any problem! just do the first( mostly named: starter) kit command and you get the wooden tools.

Map Corrupting
A player can run so far away on the map that the server generates new map. This will lag the server a lot if it is not powerful, and the map file will eventually become so big that the server does not have enough RAM to load it without horrible lag. The best way to combat this is to install anti-cheat and map limiting plugins.

Creative Destruction
With Notch releasing 1.8 another type of destruction has arrived, with the addition of creative mode (gamemode [playername] [1 or 0]) griefers can enter creative mode by an op or themselves to start a lot of destruction. Creative allows you to destroy any block so a player can bedrock his building and griefers can still grief it. This is incredibly annoying as a griefer can ruin very large portions or destroy a very big structure in a very little amount of time when in creative mode. Many creative servers will force people to wait, sign up on a website, or pass a test before being given access to creative mode because of this.

Water Flood
A Water Flood is only applicable to Creative mode, as it uses infinite water. In Alpha and Beta, an attempted flood is very easy to fix. A water flood occurs when a Griefer causes water to spill onto the level, often flooding a good part of it. Normally floods can only occur under sea level as that is the highest water can go, but it is possible to have water higher up using Map Editing. A way to combat this is to make sure Ops safe guard any potentially dangerous bodies of water with Bedrock to prevent the water escaping. Floods can also be prevented by using Sponges, which do not allow water to flow 2 blocks in any direction from the sponge. Hiding sponges in corners of rooms and other structures can prevent the structure from being flooded at all, possibly. If a small and located flood happens, the quickest solution is to gather some helpers and use Sponges to completely remove any water, then remove the sponges. Make sure no water is left behind when removing the sponges however, because 1 block of water can restart the flood again. If the flood is more large scale, have the Admin remove all the water using a Map Editor such as Omen by replacing all the water blocks with air. Another danger of this kind of griefing is the massive lag that occurs on the server during a large water flood. If the flood is large enough, all players will be kicked out of the server due to the lag.


 * As of Beta, sponges can only be obtained through inventory editing (and creative), and will not soak up any water, however some mods replenish their ability to do so.

Lava Flood
Similar to a Water Flood, a Lava block floods the area instead of water. Lava spreads far slower than water does, so if the flood is caught quickly, it can be stopped before it causes real damage. If no lava has been placed through map editing, floods can only occur deep underground where lava is. However, like water, if lava has been placed high on the map, make sure any pools of lava are protected from flooding by Bedrock. Lava floods can be very dangerous in Alpha or Beta mode for lava will set certain blocks on fire, like Wood and Trees. Lava cannot be removed with Sponges like water can, so the only way to remove it on a Creative server is to either place a block in the lava block's space, or use a map editor.

Stoning
Stoning is a method of griefing in which the griefer uses a bucket of water and a bucket of lava and pours it down a tall mountain or hill. This creates a lot of cobblestone and it is very difficult to remove it.

Repeated stoning and pillaring will form a huge volcano-like structure which not only is hard to clean up but also can infiltrate into areas protected by 3rd-party permission plugins, because they are based on authorization of block placing actions but volcano forming doesn't place blocks in protected areas.



Offensive Constructions
Some griefers grief by writing rude words or drawing offensive symbols everywhere. It's often generally harmless fun, but if a player finds it offensive they may not destroy the work, lest they become a griefer themselves. This is far less of a problem than the others, for some servers are lenient and won't care about what the griefer writes or draws.

Flattening
A relatively rare form of griefing is called Flattening. Flattening happens when a griefer begins to completely level out a map, leaving it totally flat, destroying any structures along the way. Flattening is a rare practice because it takes a long time to accomplish and is usually only done while no Ops are on the server to stop them.

Sanding / Antiquing
Using a bot to spam sand from the highest level of the map will cause the sand to settle on top of the structures below. Doing this creates a very unappealing map for most users. It is difficult to clean up.

Block Edits
Very rare, when a griefer changes one specific block type to another, ruining large sections of people's projects. This is only achievable by players with Op status, and they will have had to prove themselves to be trustworthy in order to gain these powers.

Fires
When a griefer sets a tree on fire, it will spread quickly to all nearby trees, setting the entire forest on fire within a minute. This can be extremely annoying, especially if players were leaving the forest as a permanent logging resource or decoration on the map, or if there is any flammable construction in the way. One way to prevent this type of griefing is by disabling fire spread.

Sometimes griefers target wooden structures instead, setting them on fire. The fire spreads quickly and can destroy even a larger wooden structure within seconds.

However, ever since fire was limited in Beta 1.6 (meaning it can no longer spread infinitely), this has become less of a problem. A single fire probably won't destroy an entire forest, but may still greatly damage wooden structures.

TNT Abuse
Growingly popular amongst griefers. The griefer stocks up on TNT, then places the TNT inside, around or beneath Shelters/Models of other players and sets it off, destroying everything in the process. This grief is very annoying as it leaves the land destroyed and unattractive. However, this grief is hard to perform as players would most likely notice the griefer placing TNT. This grief is currently only possible on Alpha or Beta, or on the final release(1.0.0).

"Classy" Griefing
Some people have opinions as to whether some types of griefing are more morally permissible than others. Simple TNT Abuse seems crude and doesn't have as much class as some other types of griefing such as breaking into a highly defended fortress and stealing the chests, but not their contents, undetected. Other, arguably, classy griefs include writing rude words at the height limit in 100 block tall letters; filling creations with Netherrack and lighting it; or wiring somebody else's door into the press of your own doorbell, to name a few.

Some people are happier to be griefed by classier griefs, as it has taken the griefer longer to succeed. For example, leveling out an entire continent takes more time and effort than just blowing it up with TNT. Therefore, the effort of the griefer is more appreciated, and sometimes more accepted as some players see this as a new opportunity to explore something that was generally avoided on due to the amount of work needed.

Others still take a zero-tolerance line on griefing, regardless of the amount of effort they put in, due to the fact that the griefer has still destroyed something that they took time to make themselves.

Creeping / Ghasting / Blazing / Endermen luring
A common form of griefing in SMP is deliberately luring creepers or ghasts to people's creations and making them explode. This destroys people's creations and makes the landscape look unappealing. With the introduction of the Blaze mob in 1.0, a new type of griefing called "Blazing" has been acknowledged, in which players lure Blazes into setting creations made in The Nether on fire. Due to Enderman's block picking ability, they can also be lured to people's creations to ruin their constructions. Some plugins give the option to prevent hostile mobs from targeting a player thus protecting against this type of grief. This is more likely in a beta 1.8 server because endermen can't pick up as many blocks now.

Player Jailing
Some griefers do not target structures, but players instead. In this method the griefer will dig holes around the player and make them fall into a hole, and then cover the hole up. Sometimes the griefer will fill up the hole with lava or water. This is even easier when the player is inactive. This is usually done with obsidian.

Snow Golem griefing
Because of the trails of snow that they leave behind, Snow Golems may be a new tool for griefing in the 1.0 and mass creation of such could lead to entire areas being covered in snow, spoiling the intended look of the area. In addition, their suicidal nature may quite easily lead to hostile mobs being lured towards other players.

Nether Trapping
When Beta 1.6 came out with the Nether available in SMP, a new method of trapping was introduced. First,the victim logs off, while in the Nether, then the griefer builds on top of where the victim was all the way up to the ceiling, so that when the player logs back on, he or she will be teleported to the first block they can stand at, which mean they will be teleported to the Nether's upper void. At this point, the victim can either be teleported out by an op or use a server plugin to teleport. Digging down is not an option since at the top of the Nether there is bedrock. If there is no way for you to teleport away, the only option available to you is the /kill command, which means you lose any items you had on you.

Portal Trapping (Nether Side)
A second way of trapping in the Nether involves dismantling all the Nether side portals, thus ensuring players can't leave. The griefer then uses the stolen obsidian to make a second portal to escape (often hiding it so the victim can't follow). The only other way out is for the victim to die and respawn on the overworld. Re-entering the overworld end portal will re-construct its counterpart in the Nether. (If you become a victim of this, it is possible to drop all your items, throw yourself into lava and quickly run back into the Nether to re-collect your items.)

Portal Trapping (Overworld Side)
Whilst the victim is in the Nether, the griefer builds a trap around the portal- or encases both open sides with obsidian so the player is trapped within the portal frame. Trapping the player within the frame means that he/she can't re-enter the Nether and use a different portal to escape. The best thing to do is come prepared with a water bucket and a diamond pick.

Tree Bombs
Some griefers will use trees as a trap. They will make "false" trees that resemble natural ones to lure the victim. When the victim approaches the tree he will step on a pressure plate or the griefer will pull a trigger, and the tree will blow up due to hidden TNT placed in it.

Sometimes the tree bomb is set over a wooden pressure plate, thus the log block resource falls onto it when harvested, setting off the TNT below.

SMP Diamond Bomb
This type of griefing normally includes hacking, as diamond ore cannot be collected without the use of Enchanting or Pistons. First, the griefer places diamond ore near the bottom of the map, and wires pressure plates beneath the ore to a TNT bomb. The victim will try to mine the diamond and the TNT bomb will go off, generally either killing the player or letting loose some lava.

Massacre
Killing random players excessively for no reason. Even if PvP is set to false, they can still achieve this by using wolves, Flint and Steel, TNT, Lava or suffocating players with gravel or sand. Aggressive mobs can also be used, by bringing them towards the player.

Chest Smashing
This type of griefing is common on survival servers. It is when a thief/griefer smashes a chest causing its items to spill on the floor; and with enough chests smashed, all the items on the ground will cause the server to lag horribly. Most griefers who do this are aided by an X-Ray mod. This can be prevented with chest-protection plugins. Such as lwc plugin or any other important item protection plugin.

DoS Attack
The griefer(s) may use a program (such as a client made especially for greifing or spamming) to perform a denial of service (DoS) attack on the server by flooding it with invalid UDP requests, making it lag horribly or even crash. Simple banning will not get rid of the griefers as the grief happens before they log in. The admin must ban the IP with a firewall. A firewall must be used because you must prevent the griefers packets from reaching your server. If the griefer can change their IP address, a whitelist would have to be configured for incoming IPs; this can be done with iptables for example. Unfortunately, this is an advanced solution and may be beyond the pay scale of server ops.

Tall Grass Spam
With Tall Grass introduced in Beta 1.6, Bone Meal can be used to grow a patch of Tall Grass (and occasionally flowers). This offers a new way for griefers to ruin flat grass maps, yards, spawn points, etc. Although, this type of griefing is rather easy to undo with it being very easy to destroy using Water or Fire, and has the chance of giving free seeds to the victim.

Stealing
This type of griefing is somewhat common on survival servers. Griefers will go into a house, usually when no one is around, and steal items from chests inside the house. To avoid this, players can hide chests under the floor or behind walls, but griefers can still see them if they have an X-ray mod. This is when a chest protection plugin comes into use.

Obsidian Abuse
A rare form of griefing which involves blocking off doors and mine entrances (and in some cases filling up buildings) with obsidian. This is particularly annoying as obsidian is difficult to remove. This is more common on servers which allow spawning, however a dedicated griefer can still obtain a lot of obsidian through mining. Or could use x-ray to search for diamond and then find obsidian.

Tree Spam
A rare form of griefing which involves planting saplings where they're not needed. The griefer will often use dirt blocks and bonemeal to grow trees on the side of buildings, in homes, or down mineshafts. A griefer will often place saplings next to walls and other structures higher than 2 blocks, to grow tall trees -which are harder to remove. Growing leaves also break glass and fences. However this grief also provides the victim with additional resources. (Not that it makes it less of an annoyance).

Noise
More irritating than damaging, a griefer wires multiple note blocks and doors into a redstone clock/pulser- so the notes constantly play and doors slam open and shut. A single noteblock and clock can be hidden underground, as sound can pass through any block.

Silverfish Swarming
With the introduction of silverfish, some people may place Block 97 near another stone-related blocks and destroy it causing a silverfish to pop out. The player will then attack it, causing a lot of silverfish to summon from nearby stone blocks which are then destroyed, which can cause damage to structures in a very short time. This type of griefing is uncommon due to the fact that Block 97 can only be placed by Ops, who have proven themselves to be trustworthy in order to gain their status as an Op.

Offensive/Rude
Sometimes a griefer can use a custom skin to cause offence; such as creating a fully nude skin and entering a family friendly server, or using racial stereotypes. The griefer may also draw an offensive symbol, such as the Swastika, to insult other players. Other behaviour can include using profanities in the text chat, or on signs (although both can be prevented with a plugins that either kick automatically or block such words outright). Sometimes a griefer will use signs to 'troll', leaving de-constructive comments about other players/creations. Luckily signs are easily removed, so this is rarely more than emotional hurt from a harsh critique.

Enderdragon Destruction
The Enderdragon is incredibly dangerous in the Overworld, as a single dragon can destroy structures within seconds. If lots of Enderdragons are spawned, it can annihilate an entire server. However, Enderdragons require server plugins and Op status to be spawned, but a griefer can hack them in anyways.

Piston traps
Given time and skill, a pit can be fully hidden with pistons, and opened with redstone (often trigged via pressure plate, or wired into redstone door mechanism.) This kind of trap is nearly invisible, and ranges from annoying (water pit) to deadly (lava, long fall or TNT). A well constructed trap with an escape route is often considered a socially acceptable prank, while lava is frowned upon, as the player loses his/her items.

Vine Abuse
With the Beta 1.8 Adventure Update, griefers can obtain Vines and cover structures and landscapes with them. It can take a while for the Vines to spread, but the area can become very ugly if they are left untended. This is more common in Creative Mode, as Vines are only obtainable at the Swamp biome, and the players will notice the griefer collecting the Vines and the Vines being left to spread.

Torch theft
Increasingly popular, the griefer would go to a town/house and take out all the torches, turning the area into pitch black darkness, causing zero visibility, and thus players would be unable to find their way. Also, it would cause lots of aggresive mobs to spawn, making the area a very dangerous place.

Breeding
As of 1.0, sometimes a griefer will bring passive mobs to an area and keep feeding them wheat to make them breed until the entire area is overpopulated with animals.

Egging
Similar to Breeding, egging is where the griefer stocks up on lots of eggs, then finds a house to grief and throws all the eggs in, to create a lot of chickens. This can be a problem as it is very hard to remove all these chickens and it can cause a lot of lag. However, this is quite rare.

Trunking
Trunking is when a griefer (or over zealous tree chopper) goes through a forest and only takes the easy to gather trunks of the trees leaving behind an entire forest of floating trees. This can be annoying to players who come to the forest to gather wood only to find they have to pick through the leaves to find the leftover wood.

Overkill
When a griefer goes into a PVP zone and kills everyone seen. This can be very annoying to players going in to the PVP zone for another reason then to kill players.

Mods
Mods are programs that manipulate Minecraft in a way that was not originally intended by Notch. The ability of these mods are quite debatable amongst the community. Some servers promote their use, others restrict.
 * Flying: Now in widespread use by both griefers and normal players, this is a common and easy to obtain mod that can allow griefers to easily reach tall structures and begin deconstruction of areas that will be difficult to reach by players lacking this hack. Many survival servers have plugins that automatically kick players who have been in the air for an abnormally long time (a few seconds). In fact, the server software has a setting to disallow flying.
 * X-ray Vision: A mod that allows players to find blocks and uncover minerals, hidden chests and hidden players, although some servers allow the use of this mod. There is also X-ray texture packs which work like glass. Some servers can restrict the ability of this cheat by a server mod.
 * FullBright: Allows players to see perfectly clearly, even in pitch darkness. Sometimes mobs and players are highlighted.
 * No fall damage: This hack allows players to take no fall damage when they jump from high areas, permitting griefers to quickly escape an area or cheating in server games.
 * Sneaking: This allows griefers to sneak indefinitely and move faster while sneaking, hiding the griefer's nameplate behind walls, even when chatting.
 * Speed Breaking: This allows griefers to break blocks faster than normal.
 * Kill Aura or Force Field: This causes a griefer to attack players or mobs within their proximity, allowing them to grief easier in PvP servers.
 * Nuker: This Mod allows the players to destroy blocks in a big square, used to take down a lot of houses at once. This mod is used by the pro griefers or by script kiddies who use the mod.
 * GodMode: This allows griefers to bypass nocheat for flying, and allows them to be invincible. This is mainly used on pvp servers.
 * KaiStep: This was made by Kaiemahi Vector and was used to be able to walk while not having to jump as the player step height is heigher.
 * .Crash: A mod that is rare and only the elite griefers have. Bukkit/Jeb_ patched it but there are still one or two working copies. It crashes the server.
 * SuperBuild: Made by Kaiemahi Vector, used to place blocks in a 10x10x10 box. Used for filling houses and making them solid. Used by players to help them build when modified.
 * FastPlace: Allows players to place blocks faster than normal. Used to make areas look bad, or place blocks fast.

Social Engineering
Social Engineering is when a griefer manipulates players into thinking that they are decent and trustworthy players, as well as directing the blame of griefing to someone else. This sort of griefer is significantly more dangerous than others due to their ability to blend in with innocent and trusted players. This can cause confusion throughout the server and can even cause un-deserved bans on other players. If the griefer is very dedicated to a server, they may even become an Op. When this happens, they can use their power to de-op all other ops and ban them, and can then grief as much as they please without anyone to stop them. If this worst case scenario occurs, the Admin can use operator commands through the server's console to de-op the griefer and re-op themselves.

Time
Some griefers will wait in a server, pretending to be away, or return to it when there are no ops, mods, or admins online, at which point they could destroy as much as they please until another mod, op or admin logs in. However, an op or admin can use /list or press Tab to see who is on the server and ban any known griefers.

Bots
Bots are very uncommon and sometimes attack in swarms. Not much is known about exactly how they work or their full capabilities, but bots are very dangerous and are generally only employed if a specific server has been "targeted". Bots are programs that take control of an account they've logged into and can act very human-like. It is suspected that if an Op is getting suspicious toward the bot, the hacker can speak for the bots when they are questioned. Bots come complete with many automatic actions that can instantaneously create pyramids or massive holes in any structure; they also fly around and employ random destruction griefing. IP banning and kicking are useless as the bots can switch IPs and account names in seconds and come right back. The only real defense is to shut down the server and wait until they don't come back.

 Some of the behaviors bots have been seen to exhibit are
 * Not speaking unless spoken to, such as not asking to be let out of a spawn jail.
 * Using long names (e.g., a32hr6et4u2bdjw882) that are difficult to type. With many commands from server plugins, typing only the first few characters of a username works.
 * Frequent jumping, although this is exhibited by many human players as well.
 * No clear purpose or destination, they wander (many human players do this as well, to explore the server's existing creations).
 * Sometimes, multiple bots will not have any custom skins. They may also try to "bury" players by placing blocks around them or above them to prevent escape, and then filling the small place the trapped player or players are in with lava to kill them, or with water to hinder their movement. There are multiple videos of this on YouTube happening to innocent players. Usually, other players will come along and try to free the trapped players.
 * Claiming that other players are bots and telling them to log off. This is rare.
 * Claiming that other players are bots and telling them to log off. This is rare.

Since the website was changed in September 2011, most if not all bots appear to be disabled.

Blaming
The most common thing a griefer does after his handiwork is discovered while he's not in there is to usually act innocent and point out players that were passing by the area; or those without a customized skin and/or usernames with numbers (ej. Coolguy28) since they tend to be suspicious. Lots of videos in YouTube show how griefers don't get discovered in a long time and their actions get other users banned. However, admins with a plugin that lets them see who edited blocks recently can discover the true griefer.

Griefer swarms
While one griefer can be bad, on occasions they may attack in groups. Sometimes a member of the swarm blames other griefers in the group to avoid being caught. They can also attack rapidly, typically abusing vote bans to clear out the server if vote bans exist on the server. A typical sign is about four people (four is a common vote ban threshold) joining at once, but that can be a coincidence. The swarm also provides the problem of taking longer to ban, although the server can be shut down quickly to stop any griefing. Shutting down the server is the simplest and quickest way to stop or hinder griefers. Normally the griefer swarm works as a team, and they will normally attempt to flatten a landscape by drilling through dirt on the classic maps. Some griefer swarms may even have a hacker who can flood lava across the map, typically killing any low-land players and animals. Griefer swarms can sometimes, but rarely, appear in groups of 20 or more.

Jails
Jails (also called Griefer Cells) are particularly useful. It is a small cell, made anywhere you like, made out of bedrock with a bedrock floor as well. If there are any known griefers on the server, simply get an Op to get the griefer inside then place bedrock. The griefer will then get stuck inside the jail and will not be able to get out. To let the griefer out, an Op needs to teleport the griefer to themselves. Note that (unless you use server modifications) every time you jail someone, you will have to construct a new jail,this is because,if you jail multiple players in the same cell,they may kill each other or worse yet,get themselves out by logging out and placing blocks where the other player was standing,effectively teleporting him/her to the highest available block,freeing them. Or they can just switch to creative mode if they can.

However, this method is ineffective as players can use the "/kill" command

Counter-griefing
In extremely rare occasions, griefers can also build structures like any normal Minecraft player. If the person knows who the griefer is, they can counter-grief his constructions for revenge. If the griefer is still unknown, admins can help to see who altered various blocks recently (if they have the corresponding plugin) and sometimes, the admins and/or OPs can even grief the structures themselves if the server has strict rules. However, griefing back is also seen by some users to be as bad as the original griefing, and probably will only motivate the griefer to grief even more.

Protecting
Some plugins "protect" structures within a certain area so that no blocks can be added or removed except by the original builder and/or an op or Admin. Also, these sort of plugins can prevent doors from being opened, explosions to have effect, or chests to be opened or broken. This method is particularly useful against griefers since there's a lot less options for them. However, they still can destroy the ground below the structure, or use hacks to counter this plugin. The only method against that is to quickly discover the griefer before they can actually ruin everything.

Monitoring
Some servers "hire" people to check on any new user and follow them around until the person looks reliable. These "policemen" usually have commands to aid them in case the user tried anything. However once they leave the person can start griefing. Then once again this can be fought if the admin has powers to see recent changes on the server and revert them if possible. What most admins/mods do is get a mod on bukkit (this is correct spelling) called "vanishnopacket" this lets admins be invisible at a specific time by typing /vanish.

Disabling
Most popular on Creative servers, disabling quits the ability of any new user to destroy or place blocks until given permission. The effectivity of this is high enough since most griefers only come and go to a server for a few hours or less and never come back.

Whitelisting
Useful if the server is about a small group of people. Any user who is not on the whitelist will be restricted from certain actions until he proves his reliability (which may allow the griefer to pick what things to grief and plan out their attack beforehand), or perhaps not even be allowed on the server at all.

Law system
Some servers believe in the law system and thus any person suspected of griefing will be put in a jail where he is restricted to alter any block and thus, if the person tries to flee, by leaving the server or respawning, he is banned and thus proved that he is, in fact, a griefer. However if they wait for their time on jail to end patiently, they are proven innocent. Most griefers are impatient, but so are innocent users. Often an intelligent griefer, (or user) will simply minimize the client and ignore their jail sentence,however some servers employ an anti idling plugin, kicking the player for inactivity after several minutes.

Griefer Worlds
Some Classic servers have a Griefer world, on which any Griefer is teleported to it. It is basically a room with Lava as the floor and Water as the roof and walls. These worlds generally use a bukkit plugin that makes you instantly die when touching Water and Lava, so the Griefer will get bored and leave the server. Possibly, but unlikely, a player may find the room and use buckets to gather the lava or water, and see the griefer. Occasionally they may think of the griefer as a trustworthy player, but they may recognize the griefer world and leave it alone.

Mazes
Some servers have mazes that lead to an exit at the spawn area made out of bedrock. A griefer that encounters this maze will get impatient if the maze is too difficult or has traps. Though a griefer can send a teleport request to a player that has come out of the maze if the server allows the /tp command, although if the spawn is glitchy the griefer can sometimes spawn out of the maze. This method can discourage honest players, though.

Q and A spawn
Some servers have a Q and A spawn area that asks about the servers rules which involves buttons or asked by the admin themselves. Griefers will get impatient if they keep getting the wrong answer, but this method is not very effective because the griefer can lie in the quiz and go on to ignore the rules, and honest players may be annoyed by this because they just want to build something.

Rollback
Some servers running Bukkit can use a plugin such as LogBlock, BigBrother (now discontinued), and HawkEye can find out who placed or destroyed a block. With this they can make a rollback of the griefer. If the griefer destroyed the building entirely or uses lava it might glitch out. In that case it is recommended to restore the chunks from backup.

Elements Used
Some structures can be saved or at least delay the griefer by using strong blocks such as bedrock and obsidian. This method is not commonly used. Also, if the griefer is patient then obsidian is basically useless.

Griefen Vandalisme Грифер