Tech giants 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 organization 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”.
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.
They nicknamed it the Heartbleed Bug because the flaw caused the “leak of memory contents” between servers and their clients.
It is not known whether the exploit had been used before the revelation, since doing so would not leave a trail – unless the hackers published their haul online.
“If people have logged into a service during the window of vulnerability then there is a chance that the password is already harvested,” said Ari Takanen, Codenomicon’s chief technology officer.
“In that sense it’s a good idea to change the passwords on all the updated web portals.”
Other security experts have been shocked by the revelation
“Catastrophic is the right word. On the scale of one to 10, this is an 11,” blogged Bruce Schneier.
Google warned a select number of organizations 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.
Several security companies and independent developers have published online tests to help the public discover if the services are still exposed.
However, there is no simple way to find out if they were vulnerable before.
Organizations that used Microsoft’s Internet Information Services (IIS) web server software would not have been affected.
But Codenomicon has noted that more than 66% of the net’s active sites rely on the open source alternatives Apache and Nginx, which do use OpenSSL.
Even so, some of these sites would have also employed a feature called “perfect forward secrecy” that would have limited the number of their communications that could have been hacked.
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