Due to the POODLE vulnerability in SSLv3, Authorize.net is shutting down their support for SSLv3 on Nov 4, 2014. Here's a excerpt from the notice:
To that end, on November 4, 2014, we will be disabling the use of SSLv3 within our systems. This means that if your website or shopping cart solution uses SSLv3 to send transactions to Authorize.Net, you will no longer be able to process transactions. You will also no longer be able to access any secure Authorize.Net pages from IE6.
Do the Authorize.net payment gateway plugins in CartThrob 1 or 2 use SSLv3? How can I check to make sure?