**UPDATE 2 4/12 22:37** While it appears that the Xbox Live login issues are fixed, the service is now suffering other issues that include, not being able to join parties, no access to sending or receiving messages and Friends List being totally missing. Xbox Support continues to troubleshoot the issues.
Also it appears that the outage and on-going problems are the work of hacker group ChannelZeroYT, and not Anonymous as some websites are reporting. Microsoft though continues to say that there has been no breech of the system, we’ll have more as information comes out.
**UPDATE 4/12 21:59** As per the Xbox.com Service Status page the sign-in issues that Xbox Live users have been experiencing today have been fixed. There are still on-going issues with the Xbox Live Marketplace.
If you have been having issues with Xbox Live on this wonderful Saturday, don’t worry you aren’t the only one. Microsoft is reporting that there is currently issues with Xbox Live sign ins, as well as some Xbox Live Marketplace Issues. the Xbox Support team is aware of the issues and are currently working on getting service returned to 100%. For updates check out the Xbox Live Service Status page.
We're working hard to resolve the current Xbox LIVE issue, all. Check in here: http://t.co/aGeeL5h3ya for updates! ^KE
— Xbox Support (1-5) (@XboxSupport) April 13, 2013