Spy checking

Revealing a Spy Pyro revealing an enemy Spy with the flamethrower.

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Hard ta stab a guy in da back when he's beatin' ya freakin' head in, huh? Click to listen — The Scout on anti-espionage

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Because of the Spy's ability to cloak or disguise as a character of the opposite team, it is useful to often check for the telltale signs of an enemy Spy in order to prevent them from backstabbing team-mates or sapping buildings. This is commonly known as Spy-Checking.

How to Spy-Check

Scout

Just running into everyone (since you are the fastest class) does the trick. Also Scouts using the Sandman can stun disguised spies, while the baseball will pass through friendlies. Scouts using the Force-A-Nature can launch disguised Spies that are close enough, but not actual teammates. Even at medium range, shooting a Spy with the Force-A-Nature will knock them back noticeably, allowing you to follow up with a finishing blow. Given the right circumstances, you can even push the Spy away from teammates to prevent him from backstabbing them.

Soldier

Firing a rocket into groups of allies on occasion, if any teammates are sent flying, they are a Spy. If firing a rocket at close distance it should go through a teammate. If it doesn't it might be a spy. Beware of spies if low on health, the rocket damage will almost certainly kill you first / as well.

Pyro

Periodically send a puff of flames onto your teammates. Your flames do not harm your teammates, nor do they catch flame. If they catch fire, they are a spy, so finish them! Also, the Spy will burn his team color, making it even easier to tell. This is the best and most reliable method of Spy checking. Compression blast will not knock back friendly players, but will toss Spies into the air, and can be very useful in throwing off their aim if they're about to backstab a teammate, or limiting their movements to prevent them from escaping. Your Flare Gun can also catch enemy Spies on fire, they will pass through friendlies. Against Spies using the Cloak and Dagger, igniting corners and crevices can usually uncover a Spy. Beware that the Dead Ringer can put out flames if they are ignited, so if you see a Spy that you've ignited suddenly drop dead, spray down the area with flames to ignite him again and use the compression Blast to keep him at bay until the Dead Ringer wears off.

Demoman

If one of your grenades either passes through an ally after bouncing, or blows up on an ally before bouncing, that "ally" is a Spy. If splash damage from your explosives launches an ally away, you have found an enemy spy.

Heavy

Spraying an area where a cloaked spy is thought to be is a good way to uncloak him. If a team-mate eats your dropped sandvich, and was already at full health, he is a spy, unless he is a friendly disguised spy, then he might have used it to 'heal' his disguise.

Engineer

Spies can camp by your Dispenser while cloaked for unlimited time using the standard cloaking watch or anywhere with the Cloak and Dagger, try and check the top or the surroundings of your dispenser and if you're the only Engineer on your team and if you see another Engineer coming (and if he has your name) kill him, he's a Spy! If he cant pass your Sentry Gun or Dispenser, he's a Spy!

It is also a good idea to shoot around the immediate area with your pistol to check for spies using the cloak and dagger.

Medic

Make sure you check before you start healing anyone, unless they already performed an action impossible for a Spy (i.e. shooting). Run into them if you can. If you used your ÜberCharge on someone, and they are glowing the wrong color then they are undeniably an enemy Spy If you have killed a Spy with the Übersaw and the charge hasn't increased, they are using the Dead Ringer.

Sniper

Jarate will disable a spy's cloak, so throwing it into areas where spies are thought to be can leave them vulnerable (due to the damage increase caused by Jarate). Arrows from the Huntsman will also stick to disguised spies, while simply passing through teammates. The Tribalman's Shiv makes spies bleed, which can partially disable their cloaks and expose them to everyone.

Spy

Even the spy can do a great job of spy-checking. Stab all of your teammates in the back, if you are lucky you might've stabbed an enemy spy. Also, you can cloak, and go around the map, and alerting your team of any incoming spies. As a spy, you will find your character raising his knife (just like when about to backstab an enemy) when being behind a disguised enemy spy.

Identifying enemy Spies

Signs that Indicate an Enemy Spy

• A team-mate stops when bumping into him (true team-mates pass through you) or, conversely, a team-mate which can walk through an enemy.
• A player on your team that appears to be traveling with the enemy and not being attacked (unless it's a friendly disguised Spy, though it could also be an enemy Spy disguised as a friendly Spy).
• A Scout moving at the Spy's movement speed.
• A teammate suddenly uncloaking out of nowhere. (No other class beside the Spy can turn invisible)
• Having your own name, or seeing your name yell a voice command that you didn't use.
• Having the name of somebody you know to be elsewhere or dead.
• Seeing two people in the same area that have the same name. One of them is a Spy.
• Having a name that does not correspond with the player's current class on the scoreboard. This happens when a Spy disguises himself as a class not currently on the team. It can also happen if the person has changed class while the Spy was disguised.
• Not taking any damage from enemy attacks, or plain not being fired at by the enemy. (The latter does not apply if it's a friendly disguised spy)
• A team-mate standing on a friendly sentry gun or dispenser that he didn't build. The only person that can stand on a friendly sentry or dispenser is the engineer that built it.
• While cloaked, briefly glowing his team color when bumped, shot, or bleeding.
• Obstructing friendly contact projectiles such as Rockets and Pipe bombs. Such weapons will usually shoot straight through team-mates at short distance.
• Placing Sappers on friendly buildings.
• A friendly Pyro on fire (they are normally flame-resistant).
• While cloaking or uncloaking, the spy is briefly shows his own team color until cloaking/uncloaking is complete.
• A friendly player on a control point or near a payload cart who does not seem to be capping the point or pushing the cart.
• A microphone indicator that is not connected to a body on an alltalk server - cloaked spies still display the team colored ! indicator.
• A team-mate who you can stun with the Sandman's baseball.
• A team-mate whose weapon sounds like the revolver when he reloads, making a clicking sound.
• A team-mate who is overhealed when there are no Medics on your team.
• A team-mate who is overhealed but still has less than full health (Happens when they switch disguises after being healed).
• An enemy sentry ignoring a friendly, even when the player is the closest ally to the sentry.
• Spies can charge their cloaks by picking up ammo packs and still stay cloaked. If you see health or ammo packs disappearing without anyone you can see touching them, it is a Spy.
• A teammate being healed by an enemy Medic. (Unless they are a friendly Spy, who can get enemy Medics to heal them.)
• A teammate on the opposite side of the gates during Setup. (However, they may change disguise or even change class before the round starts.)
• A friendly teammate being affected by an enemy Soldier's Buff Banner or not affected by one of your or your team-mates Buff Banners.
• A Soldier with low health equipped with the Equalizer moving at his normal speed.
• An automatic door suddenly opening without a visible player being nearby (fire around the door to uncloak the spy)

Signs that indicate a possible enemy Spy

None of these indicators are conclusive proof of a spy, but all of them would make a good time to run a spy-check:

• A Spy will want to have a backstab, so if you see someone who tries to stay behind friendlies, they may be a Spy.
• Anyone hovering near sentries or dispensers, especially if they are attempting to move behind the engineer tending them, or are at full health.
• Anyone running in an unexpected direction - a friendly Pyro, with full or nearly full health, running away from the enemies, is possibly a spy.
• Someone acting inappropriately - a Pyro who stays near the Snipers, a Demoman who is near a point, but has not placed sticky bombs, etc.
• An idle Sniper not having their rifle to their eye from a distance.
• A team-mate that deliberately avoids walking through you in tight corridors. Many spies will strafe walk and dodge other players to avoid bumping.
• A team-mate not firing at the enemy (as a Medic when your healing a team-mate, and you notice they're not firing back at the enemy bonesaw them just in case).
• An apparently injured team-mate running around the spawn area doing nothing or calling for a medic, when he could easily get health from the spawn.
• A team-mate keeping some distance from Pyros, which pose a great threat to Spies.
• Someone who hesitates before running past friendly Snipers with the Razorback.
• Someone hiding in the shadows while in friendly territory (or where no enemies can be seen).
• They fail to point out players that definitely are enemy spies, or do not spycheck. An exception is when one walks into the other. You still may want to check just in case.
• A Medic with 0% ÜberCharge. An enemy spy disguised as a medic's fake uber percentage is always 0.
• Someone who runs back when he sees you, usually still facing you.
• People calling for medic with full health, while coming into your base or otherwise.
• A team-mate that is going towards your teams intelligence room without a reason. (Usually only Spy-Checking Pyro's, Demomen with sticky launchers, Engineers and players who are carrying enemy intels have a reason to go to your intel room)
• Someone who tries to strafe-stab you (turn right when he passes above you to backstab you)
• Someone who isn't firing on the battlefield

Signs that indicate a teammate is not a Spy

• Able to be passed through a team-mate, as opposed to stopped short. Unless both of those team-mates are enemy spies.
• Shooting a weapon.
• A Scout moving at the normal Scout movement speed.
• A Scout double jumping.
• A Scout under the effects of Bonk! Atomic Punch.
• On fire and glowing your team's color.
• Entering the resupply area.
• Taunting.
• Carrying the enemy Intelligence.
• A Sniper with his Rifle to his eye (instead of holding it idly).
• A Heavy spinning his Minigun.
• A friendly player who is using their microphone: A symbol appears over the player's head. In servers with sv_alltalk enabled, the symbol is tinted red or blue according to the player's true team allegiance.
• If being fired at by enemies and is taking damage.
• Being able to pass through friendly buildings.
• Engineers carrying PDAs or toolboxes.
• A Demoman's eye is glowing from decapitating enemies with the Eyelander.
• A Soldier with a Buff Banner flag on his back.
• Spies with their Sappers out.
• Spies without a mask on (not disguised as anyone).

Proving that you are not a Spy

This is short set of ways to stop your team-mates from needlessly spy checking you.

• Shoot your weapon (a real Spy drops his disguise by attacking).
• Agree to a sequence of moves in set up time (e.g. crouching twice).
• Taunt.
• Use your voice chat to say that you are not a Spy (e.g. "Just me").
• Walk through a team-mate.
• Do anything listed under the signs that indicate that a team-mate is not a Spy

Did the Spy really die?

The Spy has the ability to feign death with one of his unlockable items, the Dead Ringer, so your Spy check may have not killed the Spy, but rather he is still alive and in your base, or worse, right behind you. Thus, it's best to know some of the signs that tell that the Spy may not really be dead.

• An enemy that dies upon the first hit. (Most players don't run in with that low health)
• An enemy Spy that suddenly stops attacking before dying on the next hit.
• Hearing the sound of a Spy uncloaking via the Dead Ringer after you killed somebody.
• A Spy that appeared as if he wanted to get himself killed. (e.g. Running undisguised into Sentry Guns or revved Heavies)
• Picking up the Spy's dropped weapon does not give you ammo or metal.
• A disguised spy lets out a death cry of the class he is disguised as when using the dead ringer. So if for example you "kill" a spy disguised as a soldier he will let out a soldier's death cry. This death cry also follows the disguised spy. If a scream appears to move, then try to follow the sound of the voice and pinpoint which direction the spy went.
• If you can't move briefly after killing a spy, he was probably trying to get past you.
• Seeing nearby health and ammo disappear.

Note: When playing Pyro, even when the corpse drops after you flare or torch them, colored team glow will still run with the Spy for a second. Use this to help alert others to the Spy, and to continue to chase and/or kill them. The Jarate also works in a similar way.