Voracian

The Voracians had an affinity for computers. They attempted to invade the planet Earth twice during the late 1990s.

Biology
Voracians' brains were mostly robotic, but organic subsystems were added; the lobes were added for extra storage and intuitive processing was controlled by the main positronics. Native Vorellan intelligence and will apparently transcended the brain and was in their whole being. Other organic parts were introduced, mostly at random and based on what was available. Some Voracians had a few organic limbs, while others were just metal brains in an organic body. Those often needed to eat and sleep, even though the very thought of that disgusted them.

Although the original Voracians were reptilian, they were experts at synthetic disguise. They possessed enhanced strength, speed and durability, although their synthetic flesh could be destroyed easily and painlessly. Injuries to their metal parts would be felt, although would only stop them for a few minutes and were easily repairable.

On Vorella
The Voracians originated on Vorella, a planet far from Earth. Its evolution paralleled Earth except that the dominant species, the Vorellans, were reptilian rather than mammallian and resembled a cross between lizards and snakes. Eventually they reached a stage in development similar to humans: utter dependence on technology. The dominant species invented advanced A.I. called Voracia. This became self-aware after only seven minutes and, within an hour, had decided that organic life wasn't efficient and should be wiped out. Although Voracia was defeated by the Vorellans when they used a pack animal to smuggle a primitive nuclear bomb to Voracia's central processing unit, before its destruction it acknowledged that organic life had its advantages, although it still believed they should be slaves of the digital life form. Prior to its final destruction, Voracia created hybrids that it called Voracians, who left Vorella for Earth.

I2
Their objective on Earth was fairly straightforward; they saw themselves as the bearers of Voracia's vision, and intended to 'liberate' all technology on the planet, i.e. make it sentient and have it rise up against the humans. To do this they set up a computer company called I2, and used this cover to create a computer program called Voractyll that could increase the power of every chip on the planet, but an MI5 agent called Kevin Sutcliffe stole it. Before the Voracians murdered him, he managed to slip the disc onto the first people he could; namely, the Fourth Doctor and Sarah Jane Smith. The Doctor and Sarah were captured by two MI5 agents who'd been monitoring the main I2 building (they'd been following Sutcliffe's murderer), but were let go after their UNIT credentials were checked up and they were vouched for by Harry Sullivan, now an agent of MI5 following his retirement from UNIT.

Attempting to find out what computers were used by I2 to let him analyse the CD's files, Harry smuggled the Doctor into the building, where he discovered that aliens were present. Sarah attempted to infiltrate I2 herself, but her attempt was seen through and she was given a pen with a tracking device in it. Fortunately it didn't interfere with the operations of MI5 and the Doctor and the truth was uncovered, but it was too late - Voractyll was on the Internet. However, the Doctor managed to track down a second version of Voractyll, which he was able to convince of the value of humanity; the two were arguing over the superiority of logic, and if the Doctor turned Voractyll off and then restarted it, it would use the same argument while the Doctor would try another tactic. Convinced of the value of humanity, the Doctor's Voractyll battled and defeated the Voracian's one, and then repaired all the damage it had done before destroying itself. The Doctor arranged for all of I2's alien technology to be destroyed, but there was one small problem; Sarah's company pen was still intact, and the Sarah of that era had kept it as a souvenir... (PROSE: System Shock)

Silver Bullet
Later on, in the last two weeks of 1999, Sarah gave Harry the pen and the Fourth Doctor arrived in a computer company during a break in. Aided by a member of the company, George Gardner, the Fourth Doctor and Harry discovered that a second group of Voracians were working undercover in a company called Silver Bullet, and had developed a chip that would actually cause the Y2K bug problem in a device that otherwise would remain functioning. They had managed to acquire a foothold in Parliament, and had persuaded the Prime Minister to stage a military coup so that he could shut off the army's funding and divert it to hospitals and other things. They had hired Lieutenant-Colonel Attiwood (a Voracian) to stage the coup, but there was also the little factor of them having given Russia the faulty equipment after they asked for some help with the bug... If the Russia computers went down when they'd taken them from Britain on simple good faith, they'd probably trigger off a nuclear holocaust.

With time running out, the Doctor learned that the Silver Bullet chips would be used to spread Voractyll across the planet. He also hit upon the idea of examining the signal generated by the pen and tracking down where it was broadcasting. His procedure was interrupted, but, with George's help, he managed to not only work out a way to neutralise the Silver Bullet chips but also to emulate the bug in otherwise unaffected systems. Taking a tank (the only definitely non-Bug-affected transport he could find), the Doctor picked up Harry and the others before heading off to 10 Downing Street, where they tricked the Prime Minister into confessing what he'd done. However, time was running out, since the Voracians would be activating Voractyll any time now. The Doctor managed to find out that they had hidden away in the PM's private residence, Chequers, but time was against him and only he and Harry could save the world...

Realising that a show of force would provoke the Voracians into activating Voractyll ahead of schedule, the Doctor and Harry went to Chequers alone, and Harry created a distraction while the Doctor broke in. The Doctor found Dave Hodges, a programmer the Voracians had converted, about to install the missing code sequences and activate the programme, and tried to reawaken his buried humanity. He was captured, as was Harry, and when Hodges refused to activate Voractyll, one of the Voracians killed him and activates it. Thanks to the Doctor's continued attempts to distract them, however, involving playing the piano and using a laughing box he gave Harry for Christmas, the Voracians had neglected to check the programme for faults. They had also realised too late that the Doctor had programmed it to emulate the Millennium Bug. The Voracians shut down or explode as the bug hit them (Since Voractyll needed to pass through them before entering the main computer network), and Voractyll was destroyed, ending the invasion. (PROSE: Millennium Shock)