Update status: Monitor for new releases of modules
The update status module periodically checks for new versions of your site's software (including contributed modules and themes), and alerts you to available updates.
The log of available updates will indicate when new releases are ready for download, and you may configure various options, including frequency of update checking and notification options, at the Update status module settings page.
Please note that in order to provide this information, anonymous usage statistics (consisting of a unique key and a list of versions of the software your site is runnning) are sent to drupal.org. Please see the drupal.org privacy policy for more information. If desired, you may disable the Update status module from the module administration page.
Note: in Drupal version 5.x, this functionality is provided outside of Drupal core by the contributed Update status module.
Disabling warning messages
My Drupal installation runs on a corporate intranet that doesn't allow access to the update data site - having the module running is pointless and slows down the installation.
I used the Update Notifications Disable (http://drupal.org/project/update_notifications_disable) module to get rid of those pesky warnings.
use proxy
For access for updates over proxy read the folloving:
http://drupal.org/node/7881