NEW YORK — Passwords, credit cards and other sensitive data are at risk after security researchers discovered a problem with an encryption technology used to securely transmit email, e-commerce transactions, social networking posts and other Web traffic.
Security researchers say the threat, known as Heartbleed, is serious, partly because it remained undiscovered for more two years. Attackers can exploit the vulnerability without leaving any trace, so anything sent during that time has potentially been compromised. It's not known, though, whether anyone has actually used it to conduct an attack.
Researchers are advising people to change all of their passwords.
"I would change every password everywhere because it's possible something was sniffed out," said Wolfgang Kandek, chief technology officer for Qualys, a maker of security-analysis software.
The flaw was found independently in recent days by researchers at Google and the Finnish security firm Codenomicon.
The breach involves SSL/TLS, an encryption technology marked by the small, closed padlock and "https:" on Web browsers to signify that traffic is secure. With the Heartbleed flaw, traffic was subject to snooping even if the padlock had been closed.
The problem affects only the variant of SSL/TLS known as OpenSSL, but that happens to be one of the most common on the Internet.
Researchers at Codenomicon say that OpenSSL is used by two of the most widely used Web server software, Apache and nginx. That means many websites potentially have this security flaw. OpenSSL is also used to secure email, chats and virtual private networks, which are used by employees to connect securely with corporate networks.
Despite the worries, Codenomicon said many large consumer sites don't have the problem because of their "conservative choice" of equipment and software. "Ironically smaller and more progressive services or those who have upgraded to (the) latest and best encryption will be affected most," the security firm added.
A fix came out Monday, but affected websites and service providers must install the update.
Many organizations were heeding the warning. Companies like Lastpass, the password manager, and Tumblr, the social network owned by Yahoo, said they had issued fixes and warned users to immediately swap out their usernames and passwords.