What are they?
Scouts are the small Thargoids, introduced in 3.0. They appear in packs, and do caustic damage. They are relatively easy to fight, though some modifications are recommended. They are very different from Thargoid Interceptors, which are far more difficult to fight.
Where are they?
Scouts scan be found in the Pleiades Nebula, the Witch Head Nebula and the bubble. From the Q4 release they can also be found (less reliably) at Wrecked Megaships.
In the Pleiades / Witch Head
Non-Human Signal Sources (NHSS) - Threat Level 3-6 tend to be increasing numbers and variants of scout. Levels 5 and 6 can also get a Thargoid Interceptor jump in. Their may also be NPCs present, which will help you in the fight. Any system in the Pleiades within around 160 Ly of Merope can spawn these NHSS, and they are more common closer to Merope. Witch Head activity is centred around 75 Ly around Witch Head Sector IR-W c1-8.
It should be noted that killing scouts in the Pleiades / Witch Head does nothing to help save systems from incursion.
Scouts can also sometimes be found via missions from Aegis Megaship and Rescue Ships near attacked systems. If the target is in the same system then this will help protect the system from further attacks.
In Systems with Incursions
These can be found via markers on the Galmap (may need to be switched on as they are off by default) or via the 2nd Galnet article in-game. Note that the galmap will show incursions even after they are defeated, so the galnet article is preferred. If the Galbet article says 'No presence' then you will not find AX CZ (though there will still be NHSS). Incursions tend to appear on Thursday, and be cleared in a few days, so are not always present.
Incursions have the usual NHSS, plus AX CZ (Combat Zones). These are a great source of scouts as new Thargoids will continually jump in. There also tend to be NPCs present who will help with the killing. AX CZ also get Interceptors jumping in, and unless you are outfitted to survive them it is best to leave when they appear. There is a trick to getting the Interceptors to not appear - if when you get the notification they are appearing you boost away from the AX CZ they will sometimes jump back out, leaving you free to kill the scouts (which continue to spawn). This technique may take a while to get right
AX CZ are great fun with multiple players, though they also tend to be 'somewhat bugged'.
Rewards for killing
Scout killing pay is poor - only 10k CR per kill. There are other benefits - scouts act as Elite foes, so combat rank gain is high and scouts are a recommended way to gain the Elite combat rank. You can also take missions from Aegis Megaships / Rescue Ships to get better CR rewards. Scouts also drop Thargoid mats, which can be collected and allow premium ammo synthesis.
You will also rank up with the Pilot's Federation, and can eventually become Allied, though there is no known benefit to this.
There are four variants : Marauder, Berserker, Inciter and Regenerator. The Xeno Scanner will allow you to detect which type(s) are present, and you can also see when they apply their special effects.
Scouts are fast moving, so an agile ship is ideal.
All scouts do caustic damage and can fire caustic missiles if you do not kill them fast. Caustic damage from missiles causes your hull to take constant damage until repaired, or the damage is burnt off by exceeded 180 degrees.
When they die the scout leaves a caustic cloud - flying through this will also cause constant damage, similar to the missiles.
The original scout type - no extra special effects.
Can fire a green pulse that increases health of all scouts within range
Can fire a white/purple pulse that causes all scouts in range to synchronise attacks and fire caustic missiles at foes (i.e. you). These will go through shields and cause constant damage until removed.
Causes more damage than regular scouts. Can fire a red pulse that causes all scouts in range to do extra damage for a time. This stacks with the Inciter effect.
These are some basic fit-out suggestions. People will have their own preferences - scouts are not that difficult to kill, and so many builds will work. There is no need to unlock any broker tech, everything you need is available from Outfitting as it was unlocked via Community Goals back in 2.4. If you want to unlock Guardian Tech then the Gauss Cannons are useful.
Useful as it will tell you what type of scout you have targeted, and also gives you the percentage health so you can avoid the caustic cloud on death. Find it here. (Note that you don't need a scanner, but they are helpful.)
These do good levels of damage against scouts. You are limited to a total of 4 AX weapons. They are available in fixed and turret (no gimbals). It is a matter of personal preference whether you use fixed or turret, though as usual fixed gives improved damage, and will be useful if you want to fight Interceptors later on. Find them here.
These will repair the caustic damage caused by scouts, and also repair the hull slightly (larger size limpet controllers are much better at hull repair). They are only practical after conflict has ended, as scouts seem to destroy them. Find them here.
An alternative is to overheat your ship to > 180% as this will burn off the corrosive material - people often fit railguns to make use of this side-effect. Overheating can be done as part of conflict, so is better for keeping the corrosion minimal.
Scouts do absolute damage, so thicker armour is better. If possible also engineer for Heavy Duty with the Deep Plating special.
Scouts do damage to shields, fitting Bi-weave will get the shields back as soon as possible. Engineer for fast recovery.
Use whatever ship you like. Bear in mind that you cannot fit more than 4 AX weapons, so a ship that can fit more is not necessarily better.
That's it - start on NHSS3 and 4, then try 5 and maybe 6 for more challenge - being prepared to run if an Interceptor appears. Oh, and if you want you can scan scouts with the Composition Scanner to help fill out your codex, but that's optional
Anything missing? Let me know in the comments