Go to profile + setting (Little picture top right)

At the bottom have a look at your twitter data?
You can see what has being accessing your twitter feed.
If an app is there that you do not use, goto the apps page and disallow it.

Now go to password and change it =)

How to mass unfollow without paying for it

Open "Following" page on Twitter (https://twitter.com/following) and scroll down till all following accounts showed in the browser.

Click middle mouse button to bring up the auto scroll.
Just pull the mose down a little to make it scroll to the very bottom of the page. Might take a while if you have thousands of follows or a slow internet connection.


Now open developer console(CTRL+SHIFT+C) on current page and paste below script on console tab.

$('.button-text.unfollow-text').trigger('click');