Canada's tax agency says it expects to have its online systems up and running again over the weekend.
The Canada Revenue Agency says it's still working on a fix to a major international security concern that forced the shutdown of its electronic filing services.
In the meantime, the agency says it is investigating whether the private information of Canadians was compromised.
The tax agency temporarily cut off public access to its electronic services today, saying the action was taken as a precaution.
The shutdown came after the Canadian Cyber Incident Response Centre issued a warning to system administrators about a coding flaw known as Heartbleed.
Other federal systems are also being assessed for their vulnerability to the threat, although it's not clear whether more online services will be taken down.
The affected services at C-R-A include EFILE, NETFILE, My Account, My Business Account and Represent a Client.
But the problem is international in scope, forcing banks, websites and social media sites to assess their vulnerability.
Heartbleed was only revealed this week, but computer experts say it's been in computer systems for the past two years.
It is a busy time of year for the tax agency, as people file returns electronically in time for the April 30th deadline.
As of the end of March, the Canada Revenue Agency had received 6.7 million returns, with 84 per cent filed electronically.
The CRA released the following statement:
The Canada Revenue Agency (CRA) places first priority on ensuring the confidentiality of taxpayer information.
After learning late yesterday afternoon about the Internet security vulnerability named the Heartbleed Bug that is affecting systems around the world, the CRA acted quickly, as a preventative measure, to temporarily shut down public access to our online services to safeguard the integrity of the information we hold. Applications affected include online services like EFILE, NETFILE, My Account, My Business Account and Represent a Client.
We are currently working on a remedy for restoring online services and, at this time, anticipate that services will resume over the weekend.
The CRA recognizes that this problem may represent a significant inconvenience for individual Canadians who count on the CRA for online information and services.
Recognizing this, the Minister of National Revenue has confirmed that individual taxpayers will not be penalized for this service interruption.
We continue to investigate any potential impacts to taxpayer information, and to be 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.
We will provide further information and daily updates at 3PM EDT on our home page.