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 a thorough inquisition made by teammates in order to determine the whereabouts of enemy Spies and eliminate them. It is important to remember that Spies cannot attack while cloaked, cannot immediately attack or place Sappers after decloaking, and can effectively kill by attacking from behind. The process is somewhat complicated since disguised Spies can use the Dead Ringer to make a hasty escape when discovered.

Identifying Spies

General Strategy

Remember that players on opposite teams cannot pass through each other. Bumping into teammates that cannot be passed through indicates that that player is an enemy Spy.

Look for teammates that are behaving bizarrely. Players in unusual positions, deliberately avoiding contact with teammates, or hiding in corners should all be Spy-checked.

Watch for teammates who are not firing their weapons or going toward resupply areas when hurt. Spies can not fire their weapon without removing their disguise, and they can not enter an enemy respawn area even when disguised.

Pay attention to the text chat. Spies will sometimes use voice commands, which will appear to all members of the opposing team as originating from the player that the Spy is disguised as. If you see voice commands originating from your name, alert teammates that the Spy is likely disguised as yourself.

Keep an eye out 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. At that time, the Spy will be shrouded with his team-colored smoke. While the smoke does not appear if the Spy is already cloaked, it will follow the Spy for a short distance if he uses it before cloaking.

If you have been killed, you can cycle through different camera angles around the map while waiting to respawn. Look out behind teammates or on open points for Spies uncloaking or disguising.

Class-specific strategies

Scout

The Scout is the fastest class. Because of this, one effective strategy is to run around the map and try to bump into fellow teammates. As noted above, any teammate that cannot be passed through is an enemy Spy in disguise.

Equip the Sandman and attempt to stun any teammates suspected to be a Spy. The baseball will stun disguised Spies, but will simply pass through teammates.

Throw Mad Milk at at a teammate to Spy-check them. Mad Milk will expose a disguised Spy, similar to Jarate.

Two close-range hits from the Scattergun, the Force-A-Nature, or three from the Shortstop will kill a Spy not equipped with the Dead Ringer.

Fire a single blast from the Force-A-Nature at close range. Spies will be severely hurt and sent flying by the blast.

Hitting a enemy Spy with the Holy Mackerel will display a notification in the kill feed.

Soldier

Fire rockets into teammates and see whether or not they are juggled by the blast. However, keep in mind that the rocket launchers have low ammo counts, so Spy-checking in this manner can burn through ammo rather quickly.

The Buff Banner, Battalion's Backup and Concheror will not affect enemy Spies, so pay attention to whether or not nearby teammates begin glowing with the appropriate particle effect by the activation of either of these three weapons.

Hitting an enemy Spy with the Disciplinary Action will not give you a speed boost.

Pyro

The Pyro's ability to set enemies on fire with incendiary weapons is perhaps the most useful tool 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. It is recommended to use only small bursts to Spy-check, as a Flamethrower requires great amounts of ammunition to function at maximum efficiency.

Compression blast is also useful in revealing Spies, as well as preventing them from accomplishing objectives. Teammates will not be affected by compression blast, so any teammate that can be juggled is a Spy.

Demoman

In close quarters, the melee weapon is probably the most effective method. In particular, the Ullapool Caber, which does not detonate on friendly players, will detonate on Spies. However, remember that the Caber will inflict 100 self-damage upon exploding.

In narrow corridors, a set of grenades from the Grenade Launcher can serve to force a Spy to clear the area or risk being discovered by blast damage. This tactic, if the Spy's Cloak is low, can force the Spy to become visible.

Placing Stickybombs with the Stickybomb Launcher on a wide area can cause Spies to hesitate about traversing such a minefield. Teammates will simply travel over the sticky trap, while most Spies will try to navigate around it.

A Demoman using the Chargin' Targe or the Splendid Screen will be stopped mid-charge when bumping into a Spy.

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. However, make sure to have ammo remaining afterwards.

If a teammate eats a dropped Sandvich and was already at full health, that player is a Spy.

Because movement speed is greatly reduced, a spun-up Heavy is a tempting Backstab target. This can sometimes be used as a goad for enemy Spies to approach.

Engineer

As an Engineer, Spies are a substantial threat, as they are able to place Electro Sappers while disguised. However, this can usually be mitigated if teammates can be asked to constantly patrol the vicinity in order to discourage Spies; this can be especially helpful if Pyros can be recruited for this task. Keep an ear out for Electro Sapper notifications; if one happens while a teammate is standing near the sapped building, that teammate is probably a Spy. Still, it's advised to Spy-check anybody that approaches your buildings with the Pistol or Shotgun, especially teammates that are approaching friendly buildings under suspicious circumstances. If any teammate is unable to pass through a Sentry Gun or Dispenser, that teammate is a Spy; the only exceptions are Engineers and their own buildings.

It is also a good idea to shoot around the immediate area with the Pistol, Shotgun or Wrangler (if equipped) to check for Spies using the Cloak and Dagger. A teammate that starts bleeding upon being hit by the Southern Hospitality is an enemy Spy. The bleeding effect will also persist when they are cloaking as well.

Medic

Medics are high priority targets for Spies. Always Spy-check a teammate that approaches while asking for healing, unless they already performed an action impossible for a Spy (e.g. shooting or passing through teammates). Remember to frequently turn around and check for approaching players from behind, as Spies love to attack Medics who are already healing another patient. If a Medic uses his Amputator taunt, disguised Spies won't glow and so a careful look can reveal a disguised Spy but as the Medic has to stand still for his taunt, there is a risk of him being backstabbed.

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 prevent a single Backstab attempt, which can be used to goad a Spy into attacking and revealing themselves, though most experienced Spies will usually resort to their Revolver when faced with such a Sniper. The Tribalman's Shiv is also useful, as it inflicts bleeding on enemy Spies, which can render their cloaks useless and expose them to teammates for elimination.

Spy

Even the Spy can do a great job of Spy-checking. The easiest way to Spy-check is to simply attack teammates from behind with the Knife; this can sometimes result in successfully backstabbing an enemy Spy. Also remember that when standing behind an enemy player, an enemy Spy disguised as a teammate, or even another cloaked Spy, the knife-raising animation will activate as if about to perform backstab. Furthermore, the Cloak and Dagger can be used to silently patrol areas for enemy Spies, who will often uncloak when no visible enemies are about. Spies positioned behind enemy lines also have a good way to watch enemy Spies disguise, allowing him to relay what class the Spy is disguised as to his team, helping them focus Spy-checks.

Revealing cloaked Spies

When cloaked, Spies will 'flicker' their team color upon being damaged or when bumping into members of the opposite team. Keep an eye out for such flickering figures who appear in the opposite team's color. Try to strafe while navigating corridors in case a Spy is trying to go through that same corridor.
- 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.
- Conversely, remember that friendly Spies will always be partially visible to teammates while cloaked.

Try to listen for the sounds of decloaking. Spies' Cloaks will emit unique sounds when cloaking and decloaking, such sounds indicate the presence of a Spy.

An ammo or health kit, or a dropped weapon that disappears without a player walking over it indicates that it was picked up by a cloaked Spy (exception: if it was a dropped weapon, it may have simply disappeared because it was not picked up in time). Spy-check the immediate area to try to reveal the Spy

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, weapons with a wide spread such as a Shotgun or Scattergun should be used to occasionally fire into corners where Spies using the Cloak and Dagger may be hiding.

As a Scout, try to throw Mad Milk into corners and crevices. It will immediately reveal any cloaked Spies and render their Cloak useless. The Scout's speed also allows players to patrol narrow corridors and bump into Spies attempting to make their way through side paths.

As a Pyro, try to randomly puff flames while patrolling, as there is always a chance that the flames 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 an ignited Spy suddenly drops 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 the Minigun where a cloaked Spy may be can prove effective in exposing (and killing) him. The Minigun has a wide spread that can reveal Spies at long range.

As an Engineer, Spies can camp by Dispensers 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 friendly buildings to counter this.
- The Wrangler is also useful for spraying down areas, similar to how the Heavy can Spy-check with the 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, check the ÜberCharge meter upon killing an enemy Spy with the Übersaw; if the charge has not increased, the Spy is 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, Jarate can short out an enemy Spy's Cloak, making them easy prey. Always try to throw Jarate into corners and crevices where Spies might be hiding before beginning sniping.

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. However, if he has the Dead Ringer equipped, it will remove the Shiv's bleeding effect.

Protecting Engineer buildings

In general, simply try to Spy-check anybody approaching a friendly 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, use Dispensers to constantly refill the Flamethrower's ammo. This can be used to either create a standing firewall that Spies cannot pass through, or as periodic stops while constantly Spy-checking the area.
- The Homewrecker can knock off enemy Electro Sappers with a single hit.

As a Demoman, the Scottish Resistance is effective at deterring enemy Spies. Simply place a few bombs around an Engineer's buildings, and detonate them when the Engineer announces 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.

Similar to the Pyro, Heavies can use Dispensers to continuously refill their Minigun ammo, allowing players to Spy-check over greater distances.

As an Engineer, always try to kill the Spy first before destroying any Electro Sappers placed on friendly buildings, as Spies will usually try to re-sap buildings immediately, or even try to kill the Engineer that is removing the Electro Sappers.
- If a Teleporter is being sapped from the Entrance, be sure not to stand on top of the Exit while destroying the Electro Sapper, as some Spies will deliberately try to telefrag players on the other side. Instead, stand next to the Teleporter Exit 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

Various team-colored indicators will immediately give away an enemy Spy:
- The flicker of a Cloak from being bumped or injured
- The fading of a Cloak while cloaking or uncloaking
- The glow from being set on fire
- The smoke from a recent use of the Disguise Kit
- The "+" particle emitted when picking up a source of health

A teammate that cannot pass through another teammate, or conversely, a teammate that has been observed walking through an enemy.

A teammate whose weapons are not glowing and crackling with electricity when a critboost occurs e.g. after an intelligence capture by your team.

A burning Pyro. Real Pyros cannot be ignited.

A teammate affected by another teammate's weapon that can cause knock back, such as compression blast and explosives.

Seeing the cloaked sihouette of a non-Spy, or seeing a non-Spy cloaking or uncloaking. Friendly Spies always appear to be Spies, no matter their current disguise; any other cloaked class must be a disguised enemy Spy.

A teammate who can't enter a friendly resupply room.

A teammate placing Electro Sappers on friendly buildings.

A friendly Engineer with the Hotrod flipped over his face but is not holding a toolbox; this is an enemy Spy holding an Electro Sapper.

A teammate standing on a friendly Sentry Gun or Dispenser, or who cannot pass through them, unless it is the Engineer who owns said building. No other team member can collide with Sentry Guns or Dispensers.

A teammate with your name.

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

A non-Spy teammate who picks up a health kit while at full health.

A teammate that is known to be dead or elsewhere (e.g. just respawned).

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

A Medic moving at the Spy's movement speed (very hard to notice but if two Medics are running side by side and one is slowly falling behind, he is a Spy).

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

A Soldier holding the Equalizer and being healed by a Medic.

A teammate who has a name that does not correspond with his or her current class on the scoreboard. This happens when a Spy disguises as a class not currently on the team. It can also happen if the person has changed class while the Spy was disguised.

A teammate that can be stunned with the Sandman's baseball.

A teammate who is 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 cart on Payload maps 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 reloading, making a single clicking sound.

A teammate who is overhealed when there are no friendly Medics on the team (unless it is a friendly Pyro who has just killed an enemy with the Powerjack, a friendly Demoman who has reached the head health limit and has just killed an enemy with Eyelander or Horseless Headless Horsemann's Headtaker or a friendly Heavy losing his 50 additional health points 30 seconds after eating a Dalokohs Bar).

A non-Spy 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.

A non-Spy teammate being healed by an enemy Medic or Dispenser.

A teammate entering/exiting the enemy resupply room.

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

The Medic's Amputator taunt buff appearing without a player, representing a cloaked enemy Spy.

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

A non-Spy teammate not under the effects of an ÜberCharge not picking up the enemy Intelligence when touching it. Or similarly, a friendly Spy who does not pick up the Intelligence while uncloaked.

A teammate using Voice chat, and a speech bubble not appearing above them.

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

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.

A Scout that doesn't double-jump.

A teammate who is in the direct firing line of an enemy but is not being fired at.

Someone who retreats backward upon seeing teammates, while still facing that teammate.

A teammate deliberately trying to avoid friendly Pyros.

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, instead of getting health from the resupply.

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

A teammate calling for a Medic while at full health, while approaching friendly forces from enemy lines.

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.
- Anyone who comes from an unexpected place - a Sniper coming from the grate in 2Fort may be a Spy that recently uncloaked.

Someone acting inappropriately - a Pyro who stays near the Snipers, a Demoman who is near a Control Point but has not placed Stickybombs, etc.

An idle Sniper with the Sniper Rifle or Sydney Sleeper who is not zoomed in (Spies cannot use the rifle's scope with their disguise).

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

A teammate that is going towards the friendly Intelligence room without a reason (Usually only Spy-checking Pyros, Demomen with Stickybomb Launchers, Engineers and players who are carrying the enemy Intelligence have a reason to go to the Intelligence room).

A teammate who takes unusual routes without reason. (e.g. Going through the gap behind the house on Dustbowl Stage 2 after the first point has been captured may suggest a Spy)

A teammate that doesn't switch weapons much or has out a weapon that is not suitable for the situation. (e.g. A Soldier with his Shovel out while trying to get past enemies)

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 teammates that you are not an enemy Spy.

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

Isn't soaked by friendly Jarate or Mad Milk.

Any usage of a weapon or item (shooting, swinging, eating, drinking, etc).
- Any usage of class-specific abilities (Scouts double jumping, Heavies spinning their Minigun, Snipers that are scoped in, etc).

A Scout moving at the normal Scout movement speed.

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

A Sniper with the Huntsman. Spies cannot hold the Huntsman while disguised.

On fire and glowing the friendly team's color.

A friendly Spy cloaking with the friendly team's color.

A player entering a friendly resupply/respawn area.

Taunting (Disguised Spies cannot taunt).

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

Being able to pass through friendly buildings save for the Engineer who built them.

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

A friendly player who is using their microphone, whose voice icon is the same color as the friendly 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, Battalion's Backup or Concheror flag on his back.

A teammate being boosted by a friendly Buff Banner, Battalion's Backup or Concheror.

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 the friendly team's 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.

A teammate who owns a headgear that has an Unusual Particle Effect attached to it.

Specific anti-Spy strategies

Main article: Anti-Spy strategy

Dealing with the Dead Ringer

The Spy has the ability to feign death with one of his unlockable items, the Dead Ringer, so always be wary upon killing enemy Spies as they may still be alive elsewhere. 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 friendly 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 a teammate approaches the 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 opponents' fire activating his feign death in order to become invisible.
- In general, if a player that has been identified to be an enemy Spy seems to be approaching a teammate 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 players 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 replenish ammo or metal. This is an easy way to double-check if a recently-killed Spy is using the Dead Ringer or not.

Spies with the Dead Ringer will not flicker when damaged or walking into enemies while cloaked for the first 6.5 seconds of the Cloak, however, they still cannot be clipped through. Being stopped while moving and not bumping into any visible objects means that a Spy whose Dead Ringer was activated is trying to pass through.

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, try to track any smoke that continues to move after an enemy Spy was killed.

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 being ignited, 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.

As a Pyro, the compression blast is the most useful tool for dealing with Dead Ringer Spies. After igniting a cloaked Dead Ringer Spy, simply push the Spy away from any ammo sources until the Cloak runs out.

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 the Spy is hiding. 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 a Spy is suspected to be 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 nearby.

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

If backstabbed by the Spy, clearly announce this to teammates, as well as the class that the Spy is now disguised as, 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 players suddenly die 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 close enough. This can serve as a key warning that a Spy might be killing teammates in the immediate vicinity.

Remember that any kills made using Your Eternal Reward will not generate kill reports for the opposite team. Pay very close attention to teammates' movements and listen for any melee hit sounds nearby.