The Infiltrator is a Strogg player class, which is able to partially stroggify Human players, using them as spies. The Infiltrator can be equipped with a Railgun and a Biolectric Pinch Bomb.
This is the only class equipped with a hacking tool, which is necessary when a Infiltrator wants to disable enemy security systems. Moreover, this function has some unique weapon types and abilities, so an Infiltrator can perform two main tasks on the battlefield – getting through the frontline in disguise and also killing enemy troops with a sniper rifle.
The Infiltrator has another interesting feature – backstabbing results in an instant kill. When he changes his appearance to that of an enemy, they cannot use most pieces of their equipment. The only weapon, whose usage does not end with demascation, is spikes. Using any firearm will cause the character to automatically revert back to their original appearance. Therefore, it is unwise to pull out a gun in front of an enemy.
Once you’re in disguise, remember that you may (even accidentally) give some clues to the enemy, from which he may be able to deduct that you’re from the opposite team. First of all, when you get tired, you start to breathe loudly, so everyone in your vicinity can hear you. Note that humans and Stroggs puff in different ways. Moreover, keep in mind that a soldier running towards the main base instead of the battlefield looks very suspicious. What is more, avoid enemy medics/field ops/technicians – if they attempt to give you a first aid/ammo bag, you won’t receive it (due to the racial difference) and that will be the signal for enemy that you’re an unwelcome guest.
One additional advantage of the disguise is the ability to walk in front of enemy antipersonnel turrets without being hurt by them.
The Infiltrator is also armed with Scrambler grenades, which turn off all electronic devices. They can be used to get past enemy turrets and to destroy mines installed by the enemy without being hurt. Unfortunately, the amount of grenades is extremely limited, so it is almost impossible to complete an objective without help from other players.