Public urged to reset all passwords

Several tech firms are urging people to change all their passwords after the discovery of a major security flaw.

The Yahoo blogging platform Tumblr has advised the public to "change your passwords everywhere - especially your high-security services like email, file storage and banking".

Security advisers have given similar warnings about the Heartbleed Bug.

It follows news that a product used to safeguard data could be compromised to allow eavesdropping.

OpenSSL is a popular cryptographic library used to digitally scramble sensitive data as it passes to and from computer servers so that only the service provider and the intended recipients can make sense of it.

If an organisation employs OpenSSL, users see a padlock icon in their web browser - although this can also be triggered by rival products.

Those affected include Canada's tax collecting agency, which halted online services "to safeguard the integrity of the information we hold".

Copied keys

Google Security and Codenomicon - a Finnish security company - revealed on Monday that a flaw had existed in OpenSSL for more than two years that could be used to expose the secret keys that identify service providers employing the code.

They said that if attackers made copies of these keys they could steal the names and passwords of people using the services, as well as take copies of their data and set up spoof sites that would appear legitimate because they used the stolen credentials.

The BBC understands that Google warned a select number of organisations about the issue before making it public, so they could update their equipment to a new version of OpenSSL released at the start of the week.

However, it appears that Yahoo was not included on this list and tech site Cnet has reported that some people were able to obtain usernames and passwords from the company before it was able to apply the fix.