LinkedIn has responded to the concerns of security experts over LinkedIn Intro, a service that attaches profile information about the sender when you receive an email. Earlier this week, security firm Bishop Fox and researchers at other companies described Intro as inherently insecure: the app essentially runs email through a LinkedIn server to analyze it, putting a potentially weak middle link between sender and recipient. But while adding another party to email always poses risks, LinkedIn says that its middle link has "the most secure implementation we believed possible."
The company doesn't directly rebut the idea that its service is a benign cousin of the "man-in-the-middle attack" used by hackers. But it promises that it's explored every possible avenue of attack and worked to protect against it, making the chances that someone could use it to compromise email account security very low. Intro, the company says, is siloed in its own part of the network, and it's limited its connection with third-party services. Internal and external security testers have tested the product and performed a "line-by-line code review."
Beyond that, LinkedIn says that email data passing through the system is heavily encrypted and stored only for a short period of time. "When mail flows through the LinkedIn Intro service, we make sure we never persist the mail contents to our systems in an unencrypted form," writes information security manager Cory Scott. "And once the user has retrieved the mail, the encrypted content is deleted from our systems."
"Once the user has retrieved the mail, the encrypted content is deleted from our systems."
Trying to clear up "inaccuracies and misperceptions" about Intro, Scott called out Bishop Fox by name: "It's important to note that we simply add an email account that communicates with Intro," he says. "We do not change the device's security profile in the manner described in a blog post that was authored by security firm Bishop Fox on Thursday." The blog post in question describes things that a security profile can grant access to: "These security profiles can do much, much more than just redirect your emails to different servers," the post reads. "A profile can be used to wipe your phone, install applications, delete applications, restrict functionality, and a whole heap of other things." This worst-case scenario appears to be what LinkedIn is denying.
Intro is, without a doubt, a third party that to some extent reads email data. The question is whether LinkedIn's security is trustworthy enough to merit using it. LinkedIn suffered a serious security breach in mid-2012, but the company is promising that Intro is held to the highest possible standard, and that the possibility for abuse in case of a serious attack is low.