Intruder Alert: Invaders Have Taken Over the Ship

In ' "," the Clickets sought to overwhelm the U.S.S. Cerritos' personnel in order to be able to harvest cloaking organs from the buhgoon, a group of spacefaring creatures.

Despite the presence of rigid security procedures and well-trained officers, there have been many other occasions in which outside forces have infiltrated Starfleet vessels and wrested control away from their crews.

With this in mind, let's look back on some of those perilous encounters and determine how the invaders managed to outmaneuver Starfleet's stringent security protocols.

Ferengi Infiltration in 's ""

An "ancient" artifact discovered by Charles 'Trip' Tucker III during a lunar survey proved to be much more than met the eye, as the canister released a gas which knocked out the ship's entire complement once it was brought onto the Enterprise NX-01.

In reality, the device had been placed there by a band of Ferengi as a means to board the vessel and pillage its valuables. The Ferengi scheme initially seemed to pay off, but Trip's requisite stay in the decon chamber isolated him from the noxious gas. Joined by the recently awakened Captain Jonathan Archer and T'Pol, Trip played on the Ferengi's greed and manipulated them into succumbing to a trap of his own. The crisis averted, the Ferengi were permitted to leave on the condition that they never approach a Starfleet or Vulcan vessel again. The Ferengi held up their end of the bargain… well, for a couple of centuries, that is.

Triannon Treachery in Star Trek: Enterprise's ""

After requesting Captain Archer's assistance with their damaged ship, Triannon religious zealots positioned themselves throughout the Enterprise and threatened to detonate organic explosives contained in their bodies. Archer reluctantly agreed to turn the vessel over to the Triannon, who intended to utilize the ship's weapons to wipe out a rival faction on their homeworld.

Fortunately, Dr. Phlox quietly developed an airborne agent that would render the organic explosives inert, and with help from a Triannon defector, it was released through the ship's environmental systems. Robbed of their advantage, the Triannon were forced to relent to Archer's demands. Upon arriving at Triannon, the zealots encountered a disturbing truth — the ongoing religious war had decimated their planet, killing millions and eradicating every major city.

Captain Angel's Attack in ' ""

A visit by Dr. Aspen to the U.S.S. Enterprise involved a vital endeavor to assist colonists stranded in deep space, but the dilemma had actually been organized by a pirate vessel called the Serene Squall. The derelict colonial ship turned out to be Serene Squall itself, and an away team's transport to the vessel had let the Enterprise's defenses down long enough for a contingent of pirates to beam over and seize the ship. The bridge crew enabled a security lockdown of the Enterprise's systems, but an unexpected enemy tricked Spock into rescinding the command.

Having pretended to be Dr. Aspen, the ruthless pirate leader Captain Angel played upon Spock's vulnerabilities as a means of negotiating the release of their beloved Xaverius, an alias used by . As devious as Angel's ruse was, its fatal flaw turned out to be the gullibility of their subordinates on the Serene Squall, who were expertly manipulated by Captain Christopher Pike.

A DaiMon's Deception in 's ""

While dealing with a situation in which Captain Jean-Luc Picard and several other crew members were accidentally transformed into children during a transporter mishap, the U.S.S. Enterprise-D conducted a search for a missing science team in the Ligos System. Suddenly, Klingon starships decloaked and inundated the ship's shields with their weapons fire.

However, rather than facing an onslaught of Klingon warriors, the Starfleet officers were boarded by a rogue Ferengi DaiMon and his underlings. Having already kidnapped the science team, the Ferengi intended to sell the ship, its crew, and the valuable minerals from the planet below on the Romulan market. With the Ferengi focused on the adults, Captain Picard rallied his fellow "children" — Ro Laren, Guinan, and Keiko O'Brien — on a clever mission to beam the Ferengi into a containment field and reassert control over the ship.

Sparring with Jem'Hadar in 's ""

As Captain Benjamin Sisko and the U.S.S. Defiant investigated a rare subspace phenomenon while tethered to one of Deep Space 9's runabouts via a tractor beam, a Dominion vessel was able to get the jump on their Starfleet counterparts by masking their approach with the vortex's radiation. Unwilling to sacrifice the runabout, the Defiant was left relatively defenseless as it tried to maintain its tractor beam lock on the auxiliary vessel. A swarm of Jem'Hadar transported onto the bridge in a flash, capturing the starship and its crew.

Meanwhile, the runabout and its complement — Jadzia Dax, Julian Bashier, and Miles O'Brien — had been subjected to the anomaly's spatial distortion and were temporarily miniaturized. The three officers exploited their disposition, flying into the still regularly proportioned Defiant's aft plasma vent and orchestrating a successful effort to retake the ship.

Seska Strikes Back in 's "" and ""

A run-in with a wounded Kazon loyal to undercover Cardassian agent Seska left Captain Kathryn Janeway naturally suspicious, yet she felt obligated to bring him aboard U.S.S. Voyager for treatment. When eight Kazon carrier ships converged on their position shortly thereafter, the Kazon patient injected himself with a hidden device and detonated himself. The explosion rocked the ship and caused a power loss, opening the door for the Kazon to begin invading the vessel through its shuttlebays.

Seska and her Kazon accomplices swiftly established their authority over the ship and deposited the captive Starfleet crew on a desolate world. Only The Doctor, Lon Suder, and Tom Paris escaped that fate, but the trio's heroic efforts resulted in the rescue of their comrades and a welcome reunion with their ship.

Macroscopic Marauders in Star Trek: Voyager's ""

On an away mission to treat a viral outbreak at a mining facility, The Doctor witnessed a macroscopic version of the virus emerge from one of his patients. Several of the organisms were accidentally beamed up along with The Doctor and infiltrated the transporter buffer before the biofilter could completely purge them from the system. The lifeforms gradually spread throughout the ship, overloading quarantine protocols and incapacitating the crew.

Upon returning to U.S.S. Voyager from her own diplomatic excursion, Captain Janeway coordinated with The Doctor on a plan to release an antigen he had concocted through the vessel's environmental systems in order to save everyone aboard. These beings were very different from the humanoid intruders that Starfleet typically dealt with, but then again, there was nothing typical about a macrovirus swarm!

Hunted by the Hirogen in Star Trek: Voyager's "" and ""

A pack of Hirogen vessels pounced on U.S.S. Voyager, breaching its hull and deploying boarding parties to claim the starship as their own. The Hirogen began to run a series of viscous hunting simulations on the holodecks, harnessing Voyager's holoprograms and using its crew as live prey. Harry Kim and The Doctor were kept outside of the holographic scenarios to help run the ship and render medical aid to those wounded in the battles, and the two intrepid officers proved to be enough to turn the tables on the Hirogen.

As additional crew members were liberated from the traumatic exercises and holographic conflicts spread throughout the ship, Voyager's complement retook the bridge and arranged a truce with their foes. In a diplomatic effort, Captain Janeway supplied the Hirogen with an optronic datacore so that they could replicate holodeck technology on their own vessels.

Captain Vadic's Vengeance in 's "" and ""

Risking the possibility of a trap, Captain Vadic and her renegade Changelings shuttled over to the apparently derelict U.S.S. Titan-A in search of Jack Crusher. While Jean-Luc Picard and the ship's crew had intentionally lured the Changelings aboard and prevailed in confining Vadic behind a force field, Lore's consciousness dominated Data's new android body long enough to lower the barriers.

Vadic and her contingent regrouped, storming through the starship and taking its command center. Devoted to delivering her quarry to the Borg Queen, Vadic was nevertheless defeated by the combined strength of a resurgent Data and a valiant scheme carried out by Jack Crusher and the Starfleet crew.

Detained by the Emerald Chain in Star Trek: Discovery's "," "," and ""

Osyraa and the Emerald Chain tracked the U.S.S. Discovery-A to the Verubin Nebula, where Sylvia Tilly served as the acting captain while Saru and Michael Burnham were on the dilithium planet below. The Discovery-A decloaked when Su'Kal nearly caused another Burn-level catastrophe, but Tilly waited until Cleveland 'Book' Booker set out to recover the away team before attempting to activate the spore drive.

Osyraa utilized the brief delay to beam her regulators onto the Discovery-A and ensnare the Federation starship with her flagship’s tentacle-like appendages. This connection allowed Osyraa's vessel to jump to Federation Headquarters along with the Discovery-A, setting in motion a cascade of events which somewhat ironically led to the demise of both Osyraa and the Emerald Chain.