A disgruntled worker put obscene messages on the website of his former employers - and also managed to delete work they were due to carry out.
Details of Paul Bacon’s hacking were given to magistrates who ordered him to carry out 120 hours unpaid work and pay £85 prosecution costs.
The court was told the missing orders caused a £3,000 loss to Woodland Property Services, which had made Bacon redundant last year.
Peter Bettany, prosecuting, said the firm described Bacon as “a nice lad, laid back” but he was released due to a lack of work.
Later the crude messages and deleted contracts were traced back to a computer used by Bacon, 27, of Main Road, Leabrooks.
When questioned, Bacon claimed he had gone into the company computer to show they had only released him because he was a union member, Southern Derbyshire magistrates heard.
Mr Bettany told the court in Derby: “He said he wanted to prove there was work but it had just not been given to him. The reason, he said, was because he was a member of the union and they didn’t like that.
Bacon pleaded guilty to a breach of the Computer Misuse Act between April 2 and 6 last year.
Lynsey Morrison, mitigating, said: “He is incredibly sorry for his actions. They occurred some time ago and since then he has had a significant amount of time to grow up and reflect on the gravity of the situation he finds himself in.
“He lost his job, his partner was expecting his first child and he was under pressure. He was struggling to understand how he was going to support his family financially,” added Miss Morrison.
The magistrates decided not to order him to pay compensation to the Derby firm but were told they could make a civil claim against Bacon, who now has a job at a call centre.