How to get accurate information about available security updates after End-of-Life?
Have a look at the myDropWizard module, a recently released module for Drupal 6. Some more details about it (from its project page, which also includes a screenprint about it):

Reports accurate update status for Drupal 6 modules now that Drupal 6 is End-of-Lifed and most contrib modules are unsupported by the community.
It does four main things:

It still shows security updates if a module is unsupported, so you'll know about security updates you haven't applied, regardless, and
It uses an alternate data source that reports whether a module is supported by the Drupal 6 Long-Term Support (LTS) vendors, so you'll know if it'll be getting security updates going foward
It will let you know about additional security updates made by the D6 LTS vendors! The LTS vendors are required to post their patches publicly, but there won't be any Security Advisories going out to let people know, and it won't be in the normal Drupal.org update status data (we create special security releases for the patches released by the LTS vendors, which appear in our data)
It integrates with Drush 7 or later. See &quot;Drush integration&quot; section below for more information!

While it uses a different data source, it continues to report usage information back to Drupal.org, so the community won't lose that valuable resource. This will let us know how many people are still using Drupal 6 in the next months and years!

Refer to &quot;Getting accurate 'Available updates' for Drupal 6&quot; for a related article about it also.