The usage of MCLeaks or AltDispenser tools (which are illegal) have been causing issues for many Minecraft users.
To correct these, remove the tool, and remove all entries containing mojang in your system's Host file. After removing it, you must change your password to avoid having your account compromised.
To edit your Host file, please do the following: Go to the Start Menu and locate notepad. Right click notepad and select Run as Administrator
Press File, then Open. Enter %SystemRoot%\System32\drivers\etc\hosts as the "File name" and press "Open"