Not a nice thing to happen, and luckily for me, when my personal Twitter Account started sending out links to money making schemes, it wasn't as bad as it could have been. But it is something you need to jump on and resolve fairly quickly to avoid losing followers, credibility or being reported (to Twitter, not Scotland Yard).
That being said, a quick bit of research and a few changes and everything was back to normal. And as we are a nice bunch at BarkWeb, I thought I would share with you that bare minimum you should do, and a quick fix, if something like this happens to you in the future.
Step 1 - Check you can still log in
Log into your account via a web browser. You can do this via your phone, but I think it's quicker using a computer and a web browser. If you can't log in, you can reset your password.
Step 2 - Change password
Once you have logged in, change your password to something more secure. Don't just add a few letters onto the end of your previous one. And remember to include numbers, letters and a symbol if you can. On a web browser, click the cog icon in the bar at the top and go to settings, then choose the password option. You'll have to check for yourself how to do this on a mobile device.
Step 3 - Delete tweets
Now that you've managed to secure, and hopefully prevent further tweets, go through and delete any tweets that you didnt send. Luckily enough this is fairly easy on any device. On a normal web browser, on your list of tweets, there is a trash icon to delete. On Andriod and iPhone, you have to click on the tweet first to view the delete icon.
Step 4 - Restrict third-part access
If your like me, then you've previously allowed other apps to access your twitter account, ie Android, mobile web, dropbox, TweetDeck etc. Now is a good time to review this. Again, go to settings and apps. Remove anything that you're suspicious of, and anything you no longer use.
Step 5 - Check your Email
Check your email account linked with your Twitter account to make sure this hasn't been compromised as well. I would also suggest changing your password for this as well, especially if its the same as your previous Twitter password.
Step 6 - Scan your computer and update everything
It's unlikely you'll find out what has actually happened to your Twitter account, but you want to prevent it happening again. It could be a virus on your computer or device, so we suggest you scan for viruses and malware. It's more likely to be a virus if you continue to post rogue posts after you have changed your password. Also best to update any device you access your Twitter acount from to make sure the latest security holes have been patched.
Conclusion and Helpful Links
Hopefully the steps you have taken above will be enough in most cases. Keep checking back every now and then to make sure everything is fine and that more tweets aren't being sent out without your knowledge.
Twitter have a page with more details about what to do and how to report things if you account has been compromised.