James Gardner was banned from harassing Hartlepool student Donna Daniels, but asked her friends to tell her to look at his website.
Some of the messages he had written indicated that 32- year-old Gardner had been secretly watching his frightened former partner.
One of them referred to a holiday to Cyprus she had booked without his knowledge – and another was about her apparent weight gain.
Deborah Sherwin, prosecuting, said the postings suggested Gardner had been stalking Miss Daniels and left her “drained and fearful”.
Teesside Crown Court was told that Gardner boasted he had used computers to find out who her friends were and would also target them.
The court heard that Gardner was prosecuted three times in six years for harassing three former girlfriends, between 2000 and 2006.
In October last year, Miss Daniels obtained a non-molestation order designed to prevent him communicating with her.
But within two months, Gardner was prosecuted for breaching the order, and was given a suspended prison sentence by magistrates.
In February, he was jailed for again breaking the conditions, and again in June for sending threatening text messages.
Days after being released, Gardner started his latest campaign of harassment, and used his MySpace page to target 20-year-old Miss Daniels.
One of the messages was: “Good job -- Cyprus is a fishing island, there’s a whale coming”, said Ms Sherwin.
In another intended for Miss Daniels’ friend, Gardner wrote: “Let her know I don’t hate her... might see her in Paphos.”
Other messages were of private and sexual natures.
Miss Sherwin told the court: “She became very worried about the messages and the fact he appeared to be watching her.”
Police raided Gardner’s home in Stockton and found a collection of things which demonstrated his obsession with Miss Daniels.
There was also a noose inside a loft hatch which he showed Miss Daniels last November, and said: “You’ll only get out of here in a body bag.”
Gardner, of Shaftesbury Street, Stockton, admitted three charges of acting in breach of a restraining order, and one of breaching a non-molestation order.
Judge Peter Fox imposed a six-month sentence, but Gardner walked free because of the time he spent on remand in custody.
Ian West, mitigating, described many of Gardner’s internet messages as “immature and juvenile” although he accepted some were worrying.
The judge told him: “You are in the habit of harassing or molesting young women.
“Maybe you don’t know who your next girlfriend will be, but if you treat her like you treated this lass, then you can expect a longer sentence.”