But Matthew Anderson, 33, will serve just half his jail term and escaped a harsher sentence.
He was a key member of an international gang who abused his skills as a computer security expert to target businesses and individuals with spam containing hidden viruses.
He controlled victims' web-cam devices remotely to see inside their homes, at one point boasting to a friend that he made a teenage girl cry by doing so.
Files he saved on his own computer included webcam images of a girl in school uniform, a family photograph of a mother and her newborn baby in hospital, and pictures of a sexual nature.
Anderson, from Keith, Banffshire, who admitted an offence under the Computer Misuse Act, appeared at Southwark Crown Court in central London.
Sentencing, Judge Geoffrey Rivlin said Anderson's offending was on an "almost unimaginable scale". He said: "Your motivation throughout, apart from the relatively small sums of money that you obtained by way of payment from the business leads, was the pleasure and satisfaction that you derived from achieving such a massive invasion into the personal lives of so many others and also the sense of power that invasion gave you.
"Whilst you may not have been engaged in fraud, it is fair to say that in an age in which computers play such an important part in the lives of so many people and businesses, an offence of this nature inevitably raises great concern and consternation."
He added: "Conduct of this kind must be deterred. Plainly only a custodial sentence is justified for an offence of this nature."
Judge Rivlin said the number of e-mails sent out by Anderson as part of the scam totalled tens of millions.
However, he said there was no evidence Anderson used the material for fraud or identity theft. Instead, the father-of-five "selectively and electively" saved personal information to his computer, the judge added.
"It's difficult to conceive of a greater invasion of privacy," Judge Rivlin said.
He added that Anderson would have faced a jail sentence twice as long had he committed the offences under the most recent law, the Police and Justice Act 2006.
Major national and international organisations, including Macmillan Publishers, car firm Toyota and the John Radcliffe Hospital in Oxford, were also targeted in what prosecutor Hugh Davies described as a "fundamental breach of security".Anderson was told he would serve half of his 18-month sentence, and was ordered to pay 5,000 costs.
The judge commended the "major" police investigation in court, saying it was "conducted to the highest standard".
In October, Anderson pleaded guilty to a charge of causing unauthorised modifications to the contents of computers between September 2005 and June 2006.
The offence was committed when Anderson was on bail for attacking the computer systems of the British National Party and the Countryside Alliance.