Online access and efiling capabilities have been temporary suspended at Canada Revenue Agency due to internet security concerns. For updates check the CRA home page at http://www.cra-arc.gc.ca/menu-e.html
Here is the current status direct from the CRA home page:
Statement from the Canada Revenue Agency
The Canada Revenue Agency (CRA) places first priority on ensuring the confidentiality of taxpayer information.
We have received information concerning an Internet security vulnerability named the Heartbleed Bug. As a preventative measure, the CRA has temporarily shut down public access to our online services to safeguard the integrity of the information we hold. Applications include online services like EFILE, NETFILE, My Account, My Business Account and Represent a Client.
The CRA recognizes that this problem may represent a significant inconvenience for individual Canadians, representatives and businesses that count on the CRA for online information and services. Please be assured that we are fully engaged in resolving this matter and restoring online services as soon as possible in a manner that ensures the private information of Canadians remains safe and secure.
Please note that consideration will also be given to taxpayers who are unable to comply with their filing requirements because of this service interruption.
We are committed to investigating any potential impacts to taxpayer information. We will provide further information and daily updates at 3PM EST on our home page until the situation is resolved.