Microsoft released security advisory 2661254 in August, announcing the availability of an update to restrict the use of digital certificates less than 1024 bits long, and recommended that customers download and install it. In October, Microsoft is expected to push the update to all computers through Microsoft Update.
This may cause issues for users trying to sign or encrypt email or access web sites with SSL certificates that have shorter keys. Other potential problems include difficulties installing applications or ActiveX controls signed with such certificates. Read more about what to expect here: