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"LinkedIn Intro is an email service that helps you be brilliant with people," according to a related overview published by LinkedIn, which also details how Google Apps administrators can block employees from using the service.
"When people email you, we show you their LinkedIn profile: you can put faces to names, write more effective emails, and establish rapport," reads LinkedIn's pitch. "You can grow your professional network by connecting with them on LinkedIn."
There's just one catch: To use the service, a LinkedIn user must route all of their emails through LinkedIn's so-called "Intro" servers, which then scan the emails for certain types of content, and -- at least temporarily -- store the passwords to users' external email accounts. "The servers use software to extract information from each message: for example, the sender's email address is extracted, so that the servers can search for their LinkedIn profile to include in the message," according to LinkedIn's overview.
[ Will the federal government like this service? Read Feds Warm Up To LinkedIn. ]
To accomplish this task, the servers may temporarily cache a user's password, presumably before generating an OpenID identifier that's then stored on the iPhone, and used to handle future authentication. "During installation, the servers temporarily cache your password in order to add a new Mail account to your device," according to LinkedIn. "Your password is only cached for the length of time it takes to install Intro, and never for more than two hours. Typically, your password is cached for no more than one minute."
But is it secure? A blog post from LinkedIn senior software engineer Martin Kleppmann is 97% a breathless explanation of how the technology -- gained via the company's 2012 acquisition of "rich contact profile" firm Rapportive -- functions, although there is a short "security and privacy" coda. "We understand that operating an email proxy server carries great responsibility," it reads. "We respect the fact that your email may contain very personal or sensitive information, and we will do everything we can to make sure that it is safe. Our principles and key security measures are detailed in our pledge of privacy."
Despite those assurances, the new LinkedIn product has raised the eyebrows of some security and privacy experts. "To give them credit, from the engineering point of view it is pretty nifty. But from the security and privacy point of view it sends a shiver down my spine," said Graham Cluley, an independent security researcher, in a blog post. In no small part, he said, that's due to the company having lost 6.5 million users' passwords last year. The breach only came to light after a hacker posted the passwords to a password-cracking forum.
But that's not the only questionable information security and privacy behavior on LinkedIn's part, he added. "LinkedIn also scooped up the contents of users' iOS calendars, including sensitive information such as confidential meeting notes and call-in numbers -- which they then transmitted in plain text, not encrypted," meaning that the information could have been easily intercepted by attackers. "LinkedIn is also, currently, the subject of a lawsuit alleging that they hacked into email accounts, in an attempt to mine address books," he said.
Others have flagged the degree of control that LinkedIn would enjoy, thanks to the technical setup. "LinkedIn Intro will Man-in-the-Middle user's IMAP connections to inject content from @LinkedIn profiles," tweeted Runa A. Sandvik, who's a core member of the Tor Project.
In other words, LinkedIn Intro inserts itself in between a user's mail client -- currently only for iOS, although the company plans to expand the service in the future -- and their email service's IMAP server, via an IMAP proxy server. Having access to a user's IMAP mailbox would also allow LinkedIn to scan all previously sent and received emails stored therein.
On the advertising front, LinkedIn's overview promises that "we will never sell, rent or give away private data about you or your contacts." Still, such scanning could be used to serve targeted advertising, as Google does, although the company appears to disavow that possibility. "Some products track the contents of your emails in order to show you advertising. LinkedIn Intro does not do that," according to the Linked Intro overview.
What LinkedIn will do, however, is watch for email recipients who aren't LinkedIn users. "If you are not connected with the person on LinkedIn, we may later suggest them as a connection on the LinkedIn website and in our other mobile apps," according to the overview.
Legally speaking, however, Google is currently embroiled in a lawsuit over its automated scanning of Gmail messages -- to serve related advertising -- based in part on the fact that it doesn't allow email senders who aren't using Gmail to opt out of the scanning. In the case of LinkedIn, it's arguably only looking for information about other LinkedIn members. But by scanning everyone's message, it might open itself up to accusations of wiretapping, as have been alleged in the consumer suit against Google.
A LinkedIn spokesman, contacted via email, wasn't immediately able to respond to an emailed request for comment about exactly what types of data Intro will collect beyond email addresses, whether it will scan emails stored on a user's IMAP server that date from before they sign up to Intro, or whether the technology underpinning the service might open LinkedIn to wiretapping charges from people whose emails are scanned, but who haven't signed up for the service.
Update -- LinkedIn has released additional information about its LinkedIn Intro program, emphasizing that it's an opt-in service. "Once you install Intro, a new Mail account is created on your iPhone. Only the email in this new Intro Mail account goes via LinkedIn; other Mail accounts are not affected in any way," it said. In addition, it noted that all related communications are fully encrypted, and that emails are only accessed when retrieved by LinkedIn from the mail server and sent to the iPhone. "LinkedIn servers automatically look up the 'From' email address, so that Intro can then be inserted into the email," it said.
A LinkedIn spokeswoman declined to address the wiretapping question.