Certificate Authority Trustwave has revoked a digital certificate that allowed one of its clients to issue valid certificates for any server, thereby allowing one of its customers to intercept their employees' private email communication.
The skeleton-key CA certificate was supplied in a tamper-proof hardware security module (HSM) designed to be used within a data loss prevention (DLP) system. DLP systems are designed to block the accidental or deliberate leaking of company secrets or confidential information.
Using the system, a user's browser or email client would be fooled into thinking it was talking over a secure encrypted link to Gmail, Skype or Hotmail. In reality it was talking to a server on the firm's premises that tapped into communications before relaying them to the genuine server. The DLP system needed to be able to issue different digital certificates from different services on the fly to pull off this approach, which amounts to a man-in-the-middle attack.
The same principle approach might be used in government monitoring activities, such as spying on its own citizens using web services such as Gmail and Skype. Evidence suggests that digital certificates issued by Netherlands-based firm DigiNotar last year were used in this way to eavesdrop on the webmail communications of Iran users last year, although no firm state-sponsored connection has been established.
In a statement published on Sunday, Trustwave said it supplied the tamper-proof digital stamp issuing device to a private customer (not an ISP, government or law enforcement agency), adding that the technology could not have been used outside the private network to which it was supplied. The CA said it had carried out an audit of the target network before supplying the technology.
Nonetheless, it admits the approach was misguided and has promised not to use the technique again. It has also revoked the offending subordinate digital credential-issuing root server.
Sysadmins applying data loss prevention policies that state that a firm has the right the scan and or block webmails sent from work can set up an internal certificate authority on machines connected to a local intranet. That approach wouldn't work on personal mobile devices a user brought into work and this seems to be the reason why Trustwave took the approach it did – which it now admits was misguided.
Trustwave has come clean and admitted it supplied technology that enabled third parties to issue arbitrary SSL server certificates for monitoring, albeit for benign reasons. This is a significant admission and further shakes confidence in the whole digital certificate trust model, already rocked by the Comodo breach, the DigiNotar hack, the SSL BEAST attack and other problems over recent months. ®