I have this message shown when I want to connect to the update server of Magento, via the connect manager. Anyone familiar with this? And how to resolve. Any tips or suggestions are welcome.
It seems some kind of suspicious activity. Was your 1.8 installation fully patched before upgrade?
You should disable the downloader on production site. Inform your you hosting provider also to check for any suspicious access to your site setup.
Check for any unknown user account in admin.
Please go through this link SECURITY BEST PRACTICES
Also, Magento is not the only way to get in. Perhaps your system haven't been updated for a while? Has tons of ports open? Runs unpatched WordPress on another virtual server?