StartSSL, a certification authority offering free SSL certificates, was compromised by unknown attackers earlier this month. The company has suspended issuing security certificates for Websites as a "defensive measure."
Attackers hit StartSSL on June 15, and the company suspended issuing SSL certificates indefinitely, according to a short statement on the site. Secure Sockets Layer is used by Websites around the world as a trust mechanism to convince the Web browser the site the user is accessing is the authentic version and not a counterfeit one. Certificates that have already been issued to customers were not compromised, and visitors to those sites are not affected, according to the statement.
Unlike the attacks on Comodo and other certificate authorities, these attackers did not gain enough access to issue valid certificates for arbitrary domains to themselves, StartSSL said. The attackers were also unsuccessful in generating an intermediate certificate that would allow them to act as their own certificate authority, The Register reported.
"Due to a security breach that occurred at the 15th of June, issuance of digital certificates and related services has been suspended. Our services will remain offline until further notice," StartSSL said.
It's not clear what the attackers were able to access, nor what it means for the company's ability to continue issuing certificates in the future.
"Our services will be gradually reinstated as the situation allows," the company said on the site. The message was still on the site as of June 22.
The company stressed that existing certificates were not compromised. More than 25,000 Websites use certificates issued by StartSSL, according to Paul Mutton, a security researcher with British security firm Netcraft.
StartSSL offers one-year free domain validated SSL certificates as well as other organization and extended validation certificates. AffirmTrust offers three-year domain validated SSL certificates for free.
The StartSSL attack follows earlier attacks on other certificate authorities and is the fifth one this year. Root certificate authority Comodo was compromised in March when an attacker breached a reseller's system and received several valid certificates for major domains. Certificates for seven addresses were forged, including Google mail, www.google.com, login.yahoo.com, login.skype.com, addons.mozilla.com and Microsoft's login.live.com.
Comodo detected the problem almost immediately and revoked the certificates before they could be used. Microsoft, Mozilla and Google pushed out updates to blacklist those certificates, but it still took a few days. Apple took much longer to update Safari.
StartSSL certificates are accepted by default by most major browsers, including Google Chrome, Mozilla Firefox and Internet Explorer. Once a certificate authority's root certificate is included within a browser, it can validate hundreds of thousands of individual Websites, making it impractical to remove the compromised authority from the browser entirely.
The attackers were after valid certificates for a list of Websites similar to those targeted by the Comodo attacker, Eddy Nigg, CTO and COO of StartSSL's parent company StartCom, told The Register. The attack did not succeed because the authority's private encryption key was stored on a computer that isn't connected to the Internet, Nigg said.
The incident highlighted the lack of security in the worldwide certificate authority structure. There were too many authorities and the system was not being implemented as designed, James Lyne, director of technology strategy at Sophos, told eWEEK. SSL no longer provides meaningful security, since users can just ignore the warning that a site has an invalid certificate and proceed to a Website, Lyne said.