Spy checking

A BLU Pyro successfully spy-checks teammates leaving their spawn on Harvest.

“

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

”

Spy-checking is the common term for when team members begin to search the area and other teammates in order to determine the whereabouts of enemy Spies. It is important to remember that Spies cannot attack while disguised, cannot immediately attack or place Sappers after decloaking, and make their kills by attacking from behind. The process is somewhat complicated by the fact that disguised Spies can use the Dead Ringer to make a hasty escape when discovered.

Spy-Checking Teammates

General

Remember that members of opposite teams cannot pass through each other. If you bump into a teammate and cannot pass through him, he is definitely a Spy.

In general, if you see a teammate behaving oddly, there is a likely chance that it is a Spy. Players in the wrong locations (such as a Pyro in the rear or a Sniper or Engineer on the front lines), deliberately avoiding contact with teammates, or hiding in corners can all be enemy Spies.

If you see your own name yell a voice command that you didn't use, it means that a Spy is disguised as you. Be sure to immediately warn your team of this, as well as your class so that your teammates know what class to look for.

Look for telltale shrouds of smoke that are colored red or blue. When a Spy uses his Disguise Kit, it takes a second for the disguise to equip, during which the Spy is shrouded with smoke of his team color. While the smoke does not appear if the disguise is used while the Spy is cloaked, it will follow the Spy for a short distance if he uses it before cloaking.

Scout

Just running into everyone (since the Scout is the fastest class) does the trick; as teammates can clip through each other, any teammate you cannot pass through is an enemy Spy in disguise. Also, Scouts using the Sandman can stun disguised Spies, while the baseball will pass through friendlies. Throwing Mad Milk at disguised Spies will expose them, allowing you and your team to easily hunt them down. Alternatively, two hits from the Scout's primary weapons will kill a Spy not equipped with the Dead Ringer, but it's less economic than simply running into them. You can also use a single blast from the Force-A-Nature at close range and see if a teammate is knocked back by it; Spies will be severely hurt and sent flying by the blast.

Soldier

There is nothing particularly special the Soldier class can do to Spy-check. The limited amount of Spy-checking a Soldier can do consists of sending a rocket into teammates to see whether the teammate is juggled by the blast or not, and occasionally pumping Shotgun blasts when it is not an inconvenience. Buff Banners and Battalion's Backups will not activate on enemy Spies, so that can be a giveaway. The rocket launchers have low ammo counts and you might not always notice disguised Spies when using the Shotgun, so generally it is a matter of analyzing behavior.

Pyro

The Pyro's ability to set enemies on fire with incendiary weapons is perhaps the most useful for detecting Spies, since only enemies can be ignited. This is the most reliable method of Spy-checking teammates. The team-colored glow produced by a burning player is especially visible when surrounding a Cloaked or Disguised Spy.

Demoman

Much like with the Soldier, the traditional Demoman is not an effective Spy-checking class. In general, your melee weapon is probably your best bet as you lack hitscan weapons.The Ullapool Caber is useful for this task, as you will instantly be able to tell when there is an enemy due to the explosion, but killing yourself is sadly possible. The Grenade Launcher has limited ammo, but is probably the most viable way to Spy-check teammates without using your melee weapon, as your grenades will detonate on a direct hit with Spies. Placing sticky bombs with your Sticky Bomb Launcher takes time, but teammates that try to avoid the bombs can be easily identified as a Spy. A Demoman using the Chargin' Targe will stop when running into a Spy while charging, and said Spy will be an easy kill.

Heavy

Heavies can attempt to Spy-check by firing their Minigun on suspicious teammates; a few seconds at close range will make quick work of an enemy Spy (make sure to have ammo to spare afterward). If a teammate eats your dropped Sandvich, and was already at full health, he is a Spy (unless he is a friendly disguised Spy, in which case he might have used it to 'heal' his disguise). A spun-up heavy is a tempting Backstab target, so even if you're busy mowing down enemies, try to find time to turn around and spycheck.

Engineer

As an Engineer, Spies are a substantial threat, able to place Sappers while disguised, but they usually aren't trouble if you can get teammates to protect your buildings (as they often are, by Pyros and teammates who need healing or ammo, or yourself). If you receive an Electro Sapper notification while a teammate is standing near the sapped building, the teammate is a Spy. Still, it's advised to Spy-check everyone with your Pistol, especially teammates approaching your buildings. If any teammate is unable to pass through your Sentry Gun or Dispenser, that teammate is a Spy.

It is also a good idea to shoot around the immediate area with your Pistol or Shotgun to check for Spies using the Cloak and Dagger. If you hit a "teammate" with the Southern Hospitality and they start bleeding, then they are a Spy. The bleeding effect will also persist when they are cloaking as well.

Medic

Medics are high priority targets for Spies. Make sure you check before you start healing anyone, unless they already performed an action impossible for a Spy (e.g. shooting). If a teammate seems suspicious to you, make sure to spycheck (attempt to clip through him, hit him with your melee weapon, etc) before healing him. Remember to frequently watch your back, as Spies love to attack Medics who are already healing another patient.

Always watch your surroundings, and be wary of any teammate that attempts to approach you from behind.

Sniper

The Sniper is very vulnerable to Spies while scoped, and is traditionally an easy Spy target, though they also have various anti-Spy weaponry that they can employ. Using Jarate on teammates will immediately reveal enemy Spies and render their Cloak useless, making them easy to identify and eliminate. Arrows from the Huntsman will also stick to disguised Spies, while simply passing through teammates. Carrying the Razorback will allow you to survive a single Backstab, and you can use this to your advantage by goading a Spy into attacking you, though most experienced Spies will usually resort to their Revolver when faced with such a Sniper. 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 may stab an enemy Spy. You will find your character raising his knife (just like when about to backstab an enemy) when standing behind a disguised enemy Spy. Also, you can Cloak and sneak around the map to alert your team of any incoming Spies. It's also a good idea to roam around your own base while disguised as an opposing enemy, as enemy Spies will rarely try to Spy-check you if you can act well.

Revealing Cloaked Spies

When Cloaked, Spies will 'flicker' their team color upon being damaged or when bumping into members of the opposite team. If you see a flickering figure of the opposite team color, it's a Spy. Try to strafe as you navigate corridors in case a Spy is trying to make his way past you.
- The Dead Ringer does not have this drawback, however it only lasts for the first 6.5 seconds of the Cloak, after which they will flicker when damaged or bumping into members of the opposite team.

Try to listen for the sounds of decloaking. Spies' Cloaks will emit unique sounds when cloaking and decloaking, so if you hear such a sound it means that a Spy is nearby.

If you see an ammo or health kit, or a dropped weapon disappearing without someone passing over it, it was picked up by a cloaked Spy. Try to Spy-check the immediate area to reveal him.

In places with bodies of water, look for floating water drop particle effects. Players exiting bodies of water will be dripping with water, so any cloaked Spies that have recently entered or exited a body of water can be easily identified by this.

An automatic door that suddenly opens without any visible player being nearby indicates a cloaked Spy passing through.

In general, if you have a weapon that has a wide spread such as a Shotgun or Scattergun, try to occasionally fire into corners where Spies using the Cloak and Dagger may be hiding.

As a Scout, try to throw your Mad Milk into corners and crevices. It will immediately reveal any cloaked Spies and render their Cloak useless. You can also use your speed to patrol narrow corridors and bump into Spies trying to Cloak their way through your base.

As a Pyro, try to randomly puff flames as you patrol your base, as there is always a chance that you will ignite a Spy trying to pass through. Puffing into corners and crevices will also usually uncover a Spy that is using the Cloak and Dagger and is waiting to recharge it. Beware that the Dead Ringer can put out flames if they are ignited, so if a Spy that you have 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 charge on his Dead Ringer runs out.

As a Heavy, spraying an area with your Minigun where a cloaked Spy may be can prove effective in exposing (and killing) him. Your Minigun has a wide spread that can reveal Spies at long range.

As an Engineer, Spies can camp by your Dispenser while cloaked for an unlimited time using the Invisibility Watch or Dead Ringer, or anywhere with the Cloak and Dagger; try and check above and around your Dispenser if you aren't already standing nearby.
- You can also use the Wrangler to control your Sentry Gun and check for Spies similarly to how a Heavy can check using his Minigun.
- The Southern Hospitality can be used to melee Spy-check as well. The bleeding effect will render a Spy's Cloak useless, forcing him to decloak and retreat.

As a Medic, if you have killed a Spy with the Übersaw and the charge hasn't increased, they are using the Dead Ringer. Be sure to keep an ear out for its distinctive decloaking noise, as Medics are high-priority targets for Spies.

As a Sniper, similar to Scouts using Mad Milk, your Jarate can short out an enemy Spy's Cloak, making them easy prey. If you think that a Spy is lying in ambush for you to start sniping, throw some Jarate first.

As with the Southern Hospitality, the Tribalman's Shiv can render a Spy's Cloak useless. Try to hit a Spy with at least one melee hit to reduce his chances of successfully escaping.

Protecting Engineer Buildings

In general, simply try to Spy-Check anybody you see approaching an Engineer's buildings. Spies trying to Sap a building will usually make a bee-line towards the building they want to Sap, so if possible try to body-block the Spy to prevent him from placing an Electro Sapper.

As a Pyro, you can use Dispensers to your advantage by using them to continually refill your ammo as you fire. You can act as a standing firewall to deter Spies from approaching at all.
- If you are carrying the Homewrecker, you can knock of enemy Sappers with a single hit. If a Spy manages to place an Electro Sapper on an Engineer's building and the Engineer is not around, you can save the building by destroying the Electro Sapper with your Homewrecker.

As a Demoman, if you are using the Scottish Resistance, simply place a few bombs around an Engineer's buildings, and detonate them when you hear an Engineer announce that his buildings are being sapped. While this may not be enough to prevent the buildings' destruction, it will at least prevent the Spy from escaping and causing more harm.

As an Engineer, always try to kill the Spy by any means necessary before unsapping your buildings, as Spies will usually try to re-sap your buildings immediately, or even try to kill you as you destroy his Sappers.
- If your Teleporter is being sapped, be sure not to stand on top of it as you knock the Electro Sapper off, as some Spies will deliberately try to telefrag you. Instead, stand next to your Teleporter and melee the first person that teleports through, as it will likely be the Spy. Furthermore, if the Spy does teleport through but dies on the first hit, he is likely using the Dead Ringer, so try to box him in and continue to attack to prevent him from escaping.

Identifying enemy Spies

Signs that Definitely Indicate an Enemy Spy

A teammate stops when bumping into another teammate (true teammates pass through each other) or conversely, a teammate that has been observed walking through an enemy.

While cloaked, briefly glowing his team color when bumped, shot, or is bleeding.

A teammate who is on fire and is glowing the enemy team's color.

When cloaking or uncloaking, a Spy that is glowing the enemy team's color.

A teammate suddenly uncloaking out of nowhere (no other class besides the Spy can Cloak). Note however, that friendly Spies will uncloak while turning your team's color.

A teammate who can't enter your resupply room.

A teammate placing Electro Sappers on friendly buildings.

A teammate standing on a friendly Sentry Gun or Dispenser, or who cannot pass through them. The only person on a team that can stand on a friendly building is the Engineer who built it.

A teammate with your name.

Seeing two people in the same area that have the same name. One of them is a Spy.

A teammate who picks up a health kit while at full health, unless it is a friendly Spy.

A teammate that you know to be elsewhere or is dead/respawning.

A Scout moving at the Spy's movement speed (in other words, moving slower than usual).

A Soldier with low health equipped with the Equalizer moving at his normal speed.

A Soldier with the Equalizer equipped that can still be healed.

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.

Obstructing friendly contact projectiles such as rockets and grenades.

A teammate that you can stun with the Sandman's baseball.

A teammate who can be injured by bolts from the Crusader's Crossbow instead of healed; when real teammates are hit by a crossbow bolt there is no impact sound.

A teammate on an uncontested Control Point or near the Payload cart who does not seem to be capping the point or pushing the cart (unless it is a RED player on an Attack/Defend map).

A microphone indicator that is not connected to a body on an alltalk server (cloaked Spies still display the team-colored "!" indicator).

A teammate whose weapon sounds like the Revolver when he reloads, making a single clicking sound.

A teammate who is overhealed when there are no Medics on your team (unless it's a friendly Pyro who has just killed an enemy with the Powerjack).

A teammate who is overhealed but still has less than full health (happens when Spies switch disguises after being healed).

A teammate being overhealed by a friendly Dispenser.

A teammate whose overheal does not appear to be decaying.

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 teammate that is being ignored by an enemy Sentry Gun, even when said teammate is the closest to the Sentry Gun and thus, most likely to be targeted (unless it's a friendly disguised Spy, although it could also be an enemy Spy disguised as a friendly Spy).

A teammate being healed by an enemy Medic (unless they are a friendly Spy, who can get enemy Medics to heal them, but again, it could be an enemy Spy disguised as a friendly Spy).

A teammate entering/exiting the enemy resupply room.

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 Battalion's Backup or is not affected by one of your or your teammates' Banners.

A friendly teammate being affected by an enemy Medic's Amputator healing effect or, conversely, not being affected by a friendly Medic's Amputator.

A circle on the ground near an enemy Medic's Amputator taunt, representing an invisible spy.

A teammate being soaked by your or a teammate's Jarate or Mad Milk, or not being affected by the enemy's.

A teammate not picking up the enemy Intelligence when touching it (unless they are currently invulnerable or a cloaked Spy).

A friendly Engineer who has the Hotrod flipped down but is not carrying a building; this is actually a Spy holding an Electro Sapper.

Signs that Possibly Indicate an 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 teammate trying to stay behind other teammates, as if trying to Backstab them.

A teammate not firing at the enemy or at all.

A teammate that deliberately avoids walking through you in tight corridors. Many Spies will strafe walk and dodge other players to avoid bumping.

Someone who runs back when he sees you, usually still facing you.

A teammate keeping some distance from Pyros, which pose a great threat to Spies.

A Medic who isn't healing anyone. Note that Spies are also slightly slower than Medics, so a sluggish Medic may be a Spy.

An apparently injured teammate running around the spawn area doing nothing or calling for a Medic, when he could easily get health from the resupply.

Someone hiding in the shadows while in friendly territory (or where no enemies can be seen).

People calling for Medic with full health, while coming into your base or otherwise.

Anyone hovering near Sentry Guns 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 Control Point but has not placed sticky bombs, etc.

An idle Sniper not having their rifle to their eye from a distance (they don't appear to be zooming in).

Someone who hesitates before running past friendly Snipers with the Razorback.

A teammate that is going towards your team's Intelligence room without a reason. (Usually only Spy-Checking Pyros, Demomen with sticky launchers, Engineers and players who are carrying the enemy intelligence have a reason to go to your Intelligence room)

Signs that Indicate a Teammate is Not a Spy

These actions prove that a Teammate is definitely not a Spy, and may also be performed to inform your Teammates that you are not a fake.

Can pass through you or a teammate, as opposed to being stopped. (Beware that both teammates may be, in fact, Spies.)

Shooting or swinging a weapon.

A Scout moving at the normal Scout movement speed.

A Scout double jumping.

A Scout under the effects of Bonk! Atomic Punch or Crit-a-Cola.

On fire and glowing in your team's color.

A friendly Spy cloaking with your team's color.

A player entering your team's resupply area.

Taunting (Disguised Spies cannot Taunt).

If being fired at by enemies and is taking damage, e.g. bleeding.

If being fired at by teammates and doesn't take damage.

Being able to pass through friendly buildings.

Carrying the enemy team's Intelligence (Also, Spies cannot disguise while holding the Intelligence).

A Sniper with his Rifle to his eye (instead of holding it idly), or with the Huntsman drawn.

A Heavy spinning his Minigun.

A friendly player who is using their microphone, whose voice icon is the same color as your team: 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.

Engineers carrying PDAs or toolboxes, or hauling a building.

A Demoman's eye is glowing from decapitating enemies with the Eyelander.

A Soldier with an active Buff Banner or Battalion's Backup flag on his back.

Spies with their Electro Sapper or Disguise Kit out.

Spies without a mask on (not disguised).

An Engineer Wrangling a Sentry Gun, but only if the Sentry Gun's laser sight is visibly following the Engineer's aim.

A Medic that is healing.

Any teammate dying and leaving a ragdoll of your team color.

A friendly player who does not get stunned by taunts or the Sandman.

A teammate who can be healed by the Crusader's Crossbow; when real teammates are hit with a friendly crossbow bolt, there is no impact sound of the arrow.

Specific Anti-Spy Strategies

Dealing with the Dead Ringer

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; 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. Spies using the Dead Ringer cannot manually Cloak, and cannot use any weapons while the Dead Ringer is out.

If an enemy dies upon the first hit while approaching your front lines without firing his weapon, it is most probably an enemy Spy disguised as one of his teammates. Most players don't run in with such low health, and a Spy disguised as a teammate will drop a corpse of the class he was disguised as.
- Similarly, if an obvious enemy Spy disguised as one of your teammates approaches your front lines from the enemy's position, he is most likely using the Dead Ringer, even if he doesn't die from the first hit. Remember that the Dead Ringer cannot Cloak at will, so a Dead Ringer Spy will rely on you activating his feign death in order to become invisible.
- In general, if a player that you have identified to be an enemy Spy seems to be approaching one of your teammates suicidally, he is probably trying to get damaged so that his Dead Ringer will be activated, so don't be fooled.

A Spy must take the time to pull out his Dead Ringer before it becomes active, and cannot attack while he has it out. If a Spy suddenly stops attacking before dying on the next hit, he is probably using the Dead Ringer.

The decloaking sound of the Dead Ringer is highly distinctive, but requires you to be within a certain radius to hear it. Try to patrol near rarely-traversed areas to ambush a Spy decloaking in an area that he thinks is safe.

Picking up the Spy's dropped weapon does not give you ammo or metal. This is an easy way to double-check if the Spy that you just killed is using the Dead Ringer or not.

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. The Dead Ringer stops Spies from flickering when damaged or walking into enemies while cloaked for the first 6.5 seconds of the Cloak.

If the Spy uses his Disguise Kit shortly before being "killed," the smoke effects will follow the Spy for the time that it takes for the Disguise to be equipped. Therefore, if you see moving smoke after killing a Spy, he is using the Dead Ringer.

Noticing that the Spy's corpse did not disappear after a few seconds.

When playing as an Engineer, if your Sentry Gun's kill counter does not increase after killing an enemy, he is probably a Spy. Remember that it may be hard to judge if the Spy was using the Dead Ringer since Sentry Guns will generally kill their targets very quickly.

When playing as a Pyro, even when the corpse drops after you ignite them, the colored team glow will follow the Spy for a second. Use this to help alert others to the Spy, and to continue to chase and/or kill them. Jarate also works in a similar way.

Dealing with the Cloak and Dagger

The Spy's Cloak and Dagger allows him to stay cloaked indefinitely, and to hide in unconventional places while waiting for the right time to strike. An area that may seem impossible for a Spy to hide in may be sheltering a particularly cunning Spy who knows where the enemy team will not check for Spies.

In general, most Cloak and Dagger Spies will try to hide in corners in order to avoid being bumped into as they recharge their Cloak. Try to occasionally fire into corners or vantage points with wide fields of view.

One brute-force method for dealing with the Cloak and Dagger is to simply repeatedly check an area where you know the Spy is. As the Cloak and Dagger has an extremely short charge meter, the Spy cannot make too many movements or their Cloak will run out.

Some unconventional Spies will hide out in the open rather than against walls or in corners. This allows them to maneuver easily to avoid detection, and easily avoids the most often checked areas of a map. Try to keep this in mind if you suspect a Spy in the area.

Dealing with Your Eternal Reward

While Spies using Your Eternal Reward cannot use their Disguise Kit at will, they make up for this by being able to quietly Backstabbing any enemies and leaving no body for their teammates to find. A Spy using Your Eternal Reward can be impossible to detect even when he is killing teammates right next to you.

Because they cannot use their Disguise Kit, simply identifying the last player that the Spy Backstabbed will let you know which player and class may be the Spy. Note that Spies with Your Eternal Reward equiped can still change their disguise weapon.

If you are Backstabbed by the Spy, clearly announce this to your team, as well as your class, to make sure that they know who the Spy is disguised as.

The Spy's victims make no sound and leave no body behind to discover, but the body is still visible for a short time before disappearing. If you see players suddenly dying noiselessly in the distance, it means that the Spy is there, so make sure to warn players as needed.

When the Spy Backstabs his victim, the faint sound of the melee hit can be heard if you're close enough. If you hear it, immediately turn and Spy-check any teammates immediately behind you.

Remember that any kills made using Your Eternal Reward will not generate kill reports for the opposite team. Pay very close attention to your teammates and listen for any melee hit sounds nearby if you suspect that a Spy is among you.