Perhaps the credentials you used for your Yahoo and kraken account were both leaked in some database for another website you registered for?

Or, the adware was, as blankcode described, enough already for an attacker to keylog your pc or your browser.

You can check some databases with your email here, https://haveibeenpwned.com to see if that's the culprit.

If not, it might be smart to completely format your harddrive. (It might be smart to do that anyway.)