Belfast Crown Court heard that Victor Garland, from Glenluce Garden, committed the offences over a month-long period in the east of the city during the summer of 2010.
He has never given a clear explanation for his actions or behaviour.
He exposed his genitals to all three female victims, one of whom was out walking when she was targeted and brought to the ground by Garland.
Another victim, a woman in her 50s, was targeted twice in her own home.
On the evening of 7 July, 2012, a woman out walking on Sydenham Avenue noticed a man on the other side of the road.
She felt suspicious and kept on walking, but as she turned into Dehra Grove, she noticed the same man on the other side of the street with his trousers down round his ankles gesturing towards her.
Garland called out to her, but she ignored him and walked on. However, Garland crossed the road and pulled the woman to the ground.
During the attack, he tried to get her on her back, attempted to pull her tracksuit bottoms down and snapped her bra strap.
Judge Corinne Philpott QC told the court "it is clear that his intention was to carry out a serious sexual assault."
The judge said this woman "suffered a trauma" and was "significantly upset by this attack."
The court heard Garland later told a probation officer that he was attracted to the woman and "experienced an uncontrollable urge".
He subsequently pleaded guilty to indecent exposure and committing an offence with intent to commit a sexual offence.
Garland also admitted three further charges of indecent exposure involving two victims.
On 24 June, 2010, a woman was jogging in the same area when she spotted a tall man walking towards her at the junction of Sydenham Avenue and Belmont Church Road.
On this occasion, Garland stood about two metres in front of her with unzipped shorts and holding his genitals in his right hand.
He also exposed himself to another woman on two separate occasions.
The woman, in her 50s, was at home when she answered a knock to her front door also on 24 June, 2010.
Garland appeared to be tying his lace and, remaining in a crouched position, he told the woman his name was Victor and he was looking for work in the area.
The occupant noticed his genitals were exposed so she told him there was no work for him, and closed the door.
He returned to her house on 22 July, when the woman spotted him standing in her garden and looking into her kitchen window with his trousers partially down, engaging in a sexual act.
She called the police and she later revealed it was her view that he knew she was at home.
Judge Corinne Philpott said two reports have been compiled on Garland, including a medical and a probation report.
In both reports, Garland gives no clear explanation for acting the way he did.
The Judge said: "There is no doubt that this is serious offending and that the risk of further offending of this nature cannot be ruled out in respect of this defendant.
"Nor can it be said that it wouldn't be imminent if the correct set of circumstances occurred."
She continued: "At this stage, the court is concerned that the defendant has gone from exposing himself to a significant sexual assault in circumstances where we do not understand his motivation."
Garland was handed a four-year extended sentence and it will be decided, by the Parole Commission, if it is suitable for him to be released after serving half his sentence.
Should he be released after two years, Garland will spend an additional four years on supervised licence.
If, however, he is deemed unsuitable for release after serving two years, he will serve the full four-year term and will spend an additional two years on supervised licence when he leaves prison.
He was also made the subject of a Sexual Offenders Prevention Order and was placed on the Sex Offenders Register.