I'm a newbie in the field of writing. After writing a book, I need to visit a number of publishers. So, how do I secure my written work from being stolen or copied before it's published? Is there any official body who regulates theft or plagiarism of written content?
If you live in America, the moment you write your first words for the story it is automatically protected under copyright law.
It is quite insulting to professional publishers to think that they would want to steal your book. Honestly and integrity is the way publishers go if they want to make a good name for the company. It just isn't good businesses to be dishonest.
Think of it this way: they would make far more of a profit making you, the writer, happy by paying you to continue making lots of books for them. Why would they want to shoot their cash cow?
Two, expecting a first or even third draft to be ready to be published before it has been proofread, edited, revised several times, edited again and read by several beta readers to find logic errors, plot errors, and loose storyline threads is pure arrogance. Sorry, but expect the reject pile if you haven't even done any of these things. The editors will not be doing your work for you, much less want to take such a rough draft.
I'm pretty sure you haven't yet or you wouldn't be so concerned about publishers stealing your "baby."
Go google: "Will a publisher steal my manuscript?"
Read up and feel better.
Just stay away from vanity publishers that try to get you to pay them and you'll be fine. Remember honest publishers will pay you.
And, in the end that's what this is really about you want to make sure that you aren't ripped off. That's fine, but consider what I said.
The best advise I've read on this it to submit to the big name publishers if you're worried.
As far as I know, you can't really protect an 'idea' (otherwise every story would have to be unique). I'm not an expert when it comes to these things, but I can imagine that it's rather simple to take an existing story, change a few names and elements, so that it counts as 'new'.
If you want to have a prove that you came up with it earlier (maybe to avoid being accused of copying the story from the one stealing it from you (which would be ironic) ), without revealing the story itself, one possibility would be to 'publish' an anagram (or even better, a hash) of your story somewhere. That way, you have a timestamp and can prove that you already had that specific draft written previously. Just make sure to not edit the text you used for the anagram or hash - otherwise it would not be possible to recreate it without knowing the changes you made.
https://wordsmith.org/anagram/practical.html (Trusted Timestamping)
As Darkocean noted, the instant you write your story, it is protected by copyright law.
"Is there any official body who can control any type of theft or plagiarism of written content?" Yes. In the United States, that would be the United States Copyright Office and the court system. Other countries have similar organizations.
Theoretically, I suppose, you could take your work to a publisher, they could put somebody else's name on it, publish it, and claim that they never heard of you. But in real life, they're not going to do this. Worrying about such things is like, well, like worrying that the bank will take your money and deny that you deposited it, or that the auto mechanic will refuse to give your car back and claim that it's his. Such crimes are possible, but only the most dishonest and fly-by-night businesses are going to try such a thing. Sooner or later they'd get caught and have to pay huge damages, maybe even go to jail. Not to belittle your efforts, but do you really think your work is so valuable that a publisher would risk going to jail rather than give you your fair share of the profits?
New authors often ask this question. My advice is: Don't worry about someone stealing your work. Worry about writing something good enough that someone would want to steal it.
All the other answers are correct: copyright law protects your work even if it's not published and even if you haven't registered it in any way. This is true in the United States, the United Kingdom, and most countries around the world.
The chances of a publisher you submit your work to will steal it are beyond slim. But copyright theft suits do happen. They're not generally against publishers whose slush pile you contributed to, but it's not impossible.
Your job, God forbid you have a case that gets that far, is to prove that you created the work before the date that someone else says they created it.
The best way to prove that you had the work on a particular date is to register it with the Copyright office before any infringement takes place. You are not required to register it to maintain your copyright, though you will have to register it before making a claim. (My information is for the U.S. but it should be similar elsewhere as there are international copyright treaties.)
Registration establishes a claim to copyright with the Copyright Office. An application for copyright registration can be filed by the author or owner of an exclusive right in a work, the owner of all exclusive rights, or an agent on behalf of an author or owner. An application contains three essential elements: a completed application form, a nonrefundable filing fee, and a nonreturnable deposit— that is, a copy or copies of the work being registered and “deposited” with the Copyright Office. A certificate of registration creates a public record of key facts relating to the authorship and ownership of the claimed work, including the title of the work, the author of the work, the name and address of the claimant or copyright owner, the year of creation, and information about whether the work is published, has been previously registered, or includes preexisting material. (ref)
If you didn't want to spend the money to register it, old advice was to send a paper copy of your manuscript in a sealed envelope through the mail to yourself, then don't open it except in court (or during a verified procedure). The postmark on the envelope would prove the date. I'd say a sealed envelope with a CD or DVD or flash drive of the work would serve the same purpose.
Except it doesn't really work. This is sometimes called "Poor Man’s Copyright" and has not been a successful defense in any case in the US, though it may help slightly in the UK. The UK copyright office also recommends registration.
Your chances of material theft from a publisher you submit your work to are very slim. But if this worries you to the point of not wanting to submit, go ahead and register the work in whatever country you are in. This will give you peace of mind that could be worth every penny, even if you never use the legal protections.