Colonial Computer History
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Partially due to traditions started during the First Cylon War, and partially to his own experience in the Cylon War, Commander William Adama maintains the order that no computers on Galactica may be networked at any time. This order surely saves Galactica and her crew when the Cylon Attack occurs. Although Galactica receives the tainted Command Navigation Program from Fleet Headquarters as did other Colonial units, Galactica cannot use it as the CNP requires a computer network; in fact, the CNP is never loaded into a computer at all. While Cylon electronic attacks disable entire Viper squadrons and damage or cripple battlestars during the Fall of the Twelve Colonies, Galactica remains up and running. However, since her munitions are previously destroyed as part of her expected decommissioning, the battlestar is initially defenseless in the opening wave of the attack, calling on her Navigation computer to perform evasive manueuvers in the first attack (Miniseries).
The evasive actions are not successful. Galactica suffers a kiloton nuclear missile strike on her forward port flight pod. The Damage Control computer determines the extent of fires and other damage, but luckily reports that very little radiation seeps through, thanks to Galactica's thick outer hull. The Damage Control computer likely provides damage information to damage control crews in coordination or by instruction of CIC as many crewmembers don fire gear to battle the blazes. However, the blazes were too intense, worsened by damage to water mains normally used for damage control. The fires threaten to ignite the ship's fuel lines. Colonel Saul Tigh activates vents throughout the port flight pod from the CIC's damage control console, releasing its atmosphere into space to extinguish the fires. Sadly, this action also causes the deaths of 85 unprepared crewmembers.
With no munitions, Galactica's Tactical Officer plots a jump through the FTL computer to Ragnar Anchorage, a Colonial munitions dump situated just inside the upper atmosphere of a large gas giant. Despite the ship not performing a Jump of any significance in 20 years, the jump is successful, and Galactica offloads a large cache of ordnance from the station.
Galactica is surrounded by at least two basestars and hundreds of Cylon Raiders at Ragnar. Fortunately, the electromagnetic storm covering the station, Galactica, and a civilian fleet of 50,000 survivors from the Colonies prevent the basestars from making a direct attack. Now armed, Galactica leads her new Fleet out of the storm, using herself as a shield while the civilian ships jump to escape the attack. The Fire Control computer and the remaining primary computers come into play at once to coordinate damage control, calculate best attack vectors, target "bogeys," and plot jumps for all civilians and the battlestar itself.
Weeks later, despite the no-networking standing order, Galactica finds herself in a situation where the FTL, Nav, DC, and Fire Control computers must be networked to greatly accelerate the needed calculations to find the civilian Fleet, which jump to a different emergency set of coordinates than the battlestar (Scattered). Without the network, Galactica would take 12 hours to calculate the proper coordinates--and the basestar in orbit around Kobol would certainly destroy them before the calculations were complete. With the inprovised network, only 10 minutes are needed for the calculations.
Lieutenant Gaeta creates software firewalls between the series of computers to resist an expected Cylon virus incursion. While the calculations were successful, the last firewall was breeched by a virus attack at the exact moment that Gaeta disconnects the network (Valley of Darkness). Shortly after, the virus shuts down many systems throughout the ship, but is fortunately stopped and removed--or so the crew believes.
Weeks later, the Cylon virus reappears in the form of a Logic bomb that had taken time to test and learn the ship's weaknesses (Flight of the Phoenix). When the next Cylon attack occurs, the Logic bomb would control all ship computers and could vent the battlestar's atmosphere to kill the crew, or direct and fire the battlestar's guns at the civilian fleet. Unfortunately, cleaning the computers require a more direct approach in the form of erasing the hard drives of each of the computers, later restoring them with backups made prior to the new Cylon war. This time-consuming action will leave Galactica a sitting duck for several minutes– time enough for the Cylon force to destroy the Fleet.
Commander Adama decides to fight one Cylon attacker with another in the form of the cooperative Caprica copy of the Cylon infiltrator Sharon Valerii. While Sharon appears wholly human, her cells were apparently light-reactive; she cut her forearm and stuck a fiber-optic cable into it, allowing her Cylon-designed brain to access the ship's communication channels and access the processing power (and the Cylon code inside of) Galactica's mainframe computer. As Galactica erases her computer hard drives, Valerii modifies the Cylon logic bomb/virus code within herself, releasing it in a broadcast to the hundreds of Cylon fighters ready to overwhelm Galactica. The broadcast contains a version of the Cylon virus which disables all the enemy's fighters, leaving Galactica's Vipers to destroy them with ease.