Google Calendar has a hole in it that is allowing spammers to put events on people's calendars. Maybe this has happened to you. You look at your Google Calendar and there is some event on there that you know nothing about, and it looks like SPAM. If this sounds like you, it's unlikely that someone has gained access to your Google calendar, it's more likely that they are exploiting this hole.

The reason for this is that when you create a calendar event, you can choose to invite other people so long as you know their GMail address. If you enter them as guests, the event will automatically show up in their calendar if their settings are configured to allow this without confirmation. The hole is that this is the default setting. So once a spammer knows your GMail address, they can add events to your calendar.

Happily the fix is easy. Just go to your Google calendar and click the Settings link, it's in the upper right-hand corner of the page. On the General tab of the settings, there is an entry called Automatically add invitations to my calendar:. You'll see that the default is set to Yes, change this to the No, only show invitations to which I have responded and then click the Save button.

Your "real" friends can still add events to your calendar, you'll just have to confirm them before they get added. And this way, the spammers will be shut down.