The Dust Walker is a Raider unit with 85 HP and is considered a Raider equivalent to a Hitman-class unit due to its high damage output towards rear and lack of overall effectiveness against armored vehicles. Its special "Contact" line of fire is called "Backstab", per Z2's 1.2 Patch notes, meaning that they can only target the rearmost unit of a column, like the Hitman.
Given their unique Backstab ability and higher chance to score a critical hit against Soldiers, players must be cautious about how they defend their rear units against Dust Walkers, all the while keeping a strong front line against all other Raiders! If you don't have Tanks yet, one way to combat their Backstabbing ability is to put your Sniper units in the middle row, while putting Riot Troopers behind them. This way, their Backstabs hit the armored Riot Troopers instead of your precious Snipers. You can also put useless, low-costing troops behind.
Prior to the 1.2 Patch and 1.1 Patch Dust Walkers were infamous for their ability to get almost constant critical hits on infantry and due to their original attack range; they were able to hit any unit regardless of placement.
As of the 1.3 Patch, they do not show up in random encounters as often as they used to, but they still retain their lethality towards most infantry. Despite its low amount of HP, Dust Walkers have a high survivability in battle due to its high chance to dodge attacks, including most shell based attacks from Tanks and sometimes even dodge Sharpshooter and Sniper fire.
Players have a chance to try these lethal assassins out during the Raiders at the Back Door mission.