Not all these platforms are reputable though, so what happens if you suddenly find yourself spamming viagara ads to all your followers?
There are a couple solutions to this problem...
Review your Twitter permissions
Login, and open up your "Settings" page, then click the "Apps" link.
This will list everything you've given permission to. If something seems fishy, just click "Revoke Access"
Even if you're not sure, it's OK to remove something, because you can always give permission again then next time you use that service.
Change your password
Giving apps permission to access your Twitter account doesn't give them administrator access to your account or tell them your security information... if you think all your apps are OK, then someone or something probably has your password.
So change it.
After you've changed it, you need to check what email you signed up to Twitter with - if you use the same password to check your email, then there's a good chance your email is compromised. Now, not only do you need to change your email password, but you have to change it at ANY website where you've used that email and password together. Fun times.