On Saturday, Microsoft Security Essentials (MSE), Microsoft’s free anti-virus software package, stopped automatically updating its malware signatures on some systems. Users are also reporting that clicking on the “Update” button on the program window likewise fails to deliver the anticipated results. The problem appears to have been present on affected systems since 19 January. Microsoft has not officially commented on the issue.
The problem can apparently be resolved by downloading the malware signatures from Microsoft’s Malware Protection Center. The signatures consists of a 70 MB program which must be run with administrator privileges. When downloading, users need to make sure they get the right executable – different packages are required for the 32- and 64-bit versions of MSE. In addition, users should also install updated network access control rules, available separately from Microsoft.