The Federation attack fighter was a type of small Federation starship utilized by civilians and Starfleet alike, as well as by Starfleet Academy, where they were used as Academy flight trainers. They were classified by Starfleet as an attack fighter, and were prominently featured during the Dominion War. (DS9: "Sacrifice of Angels")
They were first used in combat by the Maquis in 2370 during their insurrection against the Cardassian Union, when a pair of such ships were upgraded, armed, and used by the former Lieutenant Commander Calvin Hudson, in an attempted attack on a Cardassian weapons depot on Bryma. They were engaged by three Starfleet Danube-class runabouts, lead by Commander Benjamin Sisko, who forced them into a strategic retreat. (DS9: "The Maquis, Part II")
Large numbers of fighters were used by Starfleet in the Dominion War. During Operation Return, eight successive waves of fighters were sent to attack the Cardassian ships of a Dominion fleet, hoping to provoke them into breaking formation and creating an opening for the Federation fleet. (DS9: "Sacrifice of Angels") They were also present at the Second Battle of Chin'toka. (DS9: "The Changing Face of Evil")
Schematics of these vessels were included in information download package aboard the USS Voyager during the 2370s. When One was assimilating as much information as he could, the flight trainer could be seen on a screen he was learning from. It was later seen when Seven used a new device on her Borg alcove to upload information directly into her brain. (VOY: "Drone", "The Voyager Conspiracy", "Life Line")
Although not originally designed for combat, the ship that became known as the attack fighter was capable of being modified to carry an impressive arsenal. Designed for a civilian role, and sized similarly to the Starfleet runabout, the original design was only lightly armed, primarily intended for personnel and cargo transport.
When used by the Maquis, the fighters were armed with whatever weapons were available. The first examples of the ships used by the Maquis were armed with Pygorian weapons, including photon torpedoes, pulse cannons, ship-mounted high-energy disruptors and particle accelerators; these were used when an attack was planned at a weapons depot on the Bryma colony. (DS9: "The Maquis, Part II") Captain Keogh referred to these vessels as "lightly armed shuttlecraft," compared to the Dominion ships he expected to face in the Gamma Quadrant. (DS9: "The Jem'Hadar")
Ships of the class
The fighter cockpit interior, seen in "The Maquis, Part II", was a modification of the Type 15 shuttlepod set. It was reused later from the Deep Space Nine episode "The Search, Part I" onwards to represent the Type 18 shuttlepod cockpit.
The script of "Sacrifice of Angels" stated that the attack fighters were firing a barrage of quantum torpedoes when attacking the Dominion lines.  The effects used for the phasers and quantum torpedoes of the fighters in this episode were not what was normally associated with these Starfleet weapons. The torpedo launchers were mounted on the wings and on the nose of the ship. In some shots, the wing torpedoes seem to be launched from the same spot where the pulse cannons were located in "The Maquis, Part II." In others, they seemed to be coming from the three small visible tubes on each of the wings. These tubes would seem to be much too small to launch full-sized torpedoes.
The term "attack fighter" was used to describe these vessels in "Sacrifice of Angels" and "What You Leave Behind", in the latter of which, they were also called simply "fighters"; they were also called "Federation fighters" in the former reference, as well as in "The Changing Face of Evil". An image depicting the port profile of the craft, was originally created by Doug Drexler, where it originally appeared in the Star Trek Encyclopedia (2nd ed., p. 1), accompanying the main entry "Academy Flight Range" – though incorrectly depicting the Academy trainer craft that appeared in the Star Trek: The Next Generation episode "The First Duty", specifically Locarno's ship. This image and label continued to be used in the Encyclopedia's third (p. 1) and fourth editions (vol. 1, p. 9). This mislabeled image also appeared on numerous LCARS screens (as noted in the appearances listed above with a †) throughout Deep Space Nine and Voyager. According to Sternbach, the reason for this was because "[t]here was some editorial confusion over which little ship was the trainer." 
According to Issue #68 of the Star Trek: The Official Starships Collection, the Federation attack fighter was approximately 25 meters in length, had a maximum speed of warp factor 9, and a crew complement of 2.