Video report by ITV news correspondent Ben Chapman
There could be as many as 190 potential victims of the "UK's most prolific rapist", police have warned.
Specialist officers and victim support are on standby to help anyone who may have been approached by Reynhard Sinaga who was convicted of 159 offences against 48 men on Monday.
But police say the number could rise as they warn there are still as many as 70 individuals who they have not been able to identify.
The "depraved sexual predator" convinced many of his victims - usually young, drunk students - he had done them a favour by offering them a floor to sleep on for the night.
From the vantage point of his Manchester city centre apartment, he targeted lone young men who were worse for wear from alcohol and had become separated from friends or were on their way home after a night out.
Once at his flat, he would offer his victim a spiked drink that would render them unconscious.
He would then film himself sexually assaulting the men.
The "very, very difficult" operation to convict Sinaga saw police officers trawling through almost three terabytes of data - the equivalent of watching 1,500 DVD films - of clips found on Sinaga's phones in order to identify victims.
The men were often unaware of the full horror of what had happened to them until they were contacted by officers.
CCTV footage shows the 36-year-old mature student prowling the streets looking for victims.
None of the victims felt intimidated by Sinaga - slight in stature and friendly by appearance.
One said Sinaga was "really nice" and "looked after him" after he lost his friends and his phone battery had ran out.
Another thought the defendant had acted as a Good Samaritan after Sinaga claimed to have looked after him when he found him lying on the ground near a hotel.
Manchester Crown Court heard one complainant was sitting on the kerbside after the battery on his mobile phone was drained and he was approached by Sinaga.
The defendant invited him to his apartment to charge the device but instead went on to drug and sexually violate him on camera.
Several of his victims felt guilty when they awoke the next day for troubling a stranger who they thought had provided them with somewhere to stay or for being sick in his flat.
Others felt they had undergone a "weird experience" but none had any real concerns or suspicions, with one complainant telling the court: "I thought briefly he might have done something, but I thought stuff like that doesn't happen."
Two victims attempted to commit suicide as a result of severe depression.
Assistant Chief Constable Mabs Hussain described Sinaga as a "depraved sexual predator" who had taken advantage of trusting young men.
"We have specialist officers waiting, we have a helpline where the numbers are available and we are working with specialist victim support services including St Mary's Sexual Assault Referral Centre, Survivors Manchester and Victims' Services," he said.
"At the forefront of this investigation and our primary objective throughout has been to provide the support to the victims and I would encourage them to come forward.
"We have the specialist services to provide that support."
He said police believed Sinaga to be "the UK's most prolific rapist".
"The reason I say that is because on the information and evidence we suspect there are in total 190 victims approximately who have been involved," he added.
Assistant Chief Constable Hussain praised the bravery of the victims whose statements had helped convict Sinaga, ."I think we need to concentrate less on Reynhard Sinaga as an individual and focus much more on each individual victim who has either supported the prosecution or provided evidence and information.
"I cannot begin to imagine what they have had to endure, what they have had to go through and what they are still living with today."
If you wish to speak to police and make a report relating to Reynhard Sinaga, then please contact 0800 092 0410 (calls made from within the UK) / 0207158 0124 (international calls).