Two "predatory" paedophiles, one of whom is HIV positive, have been jailed for life.
Police described the crimes of Anthony Marsh, 53, and his accomplice Lee Davis, 39, as "vile, horrendous offences".
Marsh, a HIV positive paedophile, was jailed for life and told he must serve at least ten years before he is considered for release. Lee Davis was also given a life term and told he must serve at least 12-and-a-half years in prison.
Sentencing the men, Judge Julian Goose QC told Marsh and Davis they were "predatory, dangerous paedophiles".
The court heard that the two men, who are both married with children, led 'double lives'. The pair used social networks, such as Bebo and Facebook, as well as specialist gay websites to groom boys.
After grooming teenagers as young as 13 online, salesman Marsh and unemployed Davis met their victims and sexually abused them. Police found a library of films hidden in the cellar of Davis's home showing him abusing the boys. Officers also established that Marsh distributed some footage shot by Marsh over the web.
The two men admitted more than 50 child sex offences involving young boys, who all subsequently tested negative for HIV.
Speaking outside court, Detective Inspector Delphine Waring, of South Yorkshire Police, said: "Today's sentencing brings to a conclusion one of the most shocking series of sexual crimes committed against young boys that South Yorkshire Police has investigated.
"Marsh and Davis indulged their own depraved and criminal desires for many years against a number of young, impressionable and vulnerable young boys the length and breadth of the country.
"The extent of their offending was matched only by the duplicity of their behaviour, which included their use of pseudonyms and multiple mobile phones to disguise their true identities and the deceit they exhibited day after day to their own families." Ms Waring said Marsh's crimes were "especially deplorable".
"Knowing he had HIV, he chose to engage in sexual conduct with teenage boys and, in so doing, demonstrated a complete disregard for their wellbeing and future health.
"But, for Marsh and Davis's victims and their own families, today's sentencing will not be the end of the story.
"The damage these two men have inflicted will last for many years to come."
The detective said it was possible more victims had not yet identified themselves and urged any people in that position to come forward for help.
The two men were caught after Mr Marsh was arrested in May 2012 at a hotel in North Yorkshire, when he was spotted with indecent images of children. In Marsh's possession were found images of the highest possible level of seriousness including photographs of sado-masochistic sex with children as young as six, sometimes involving animals.
The offences admitted by Marsh and Davis started in 2004 when Marsh was already diagnosed HIV positive.
Judge Goose said it was "truly shocking" Marsh had unprotected sex with young, vulnerable victims knowing his condition.
He told the defendant he carried on "never for a moment telling most of them, any of them, of your diagnosis or telling them of the risk they were taking." The judge said to them: "You are both predatory, dangerous paedophiles."