LinkedIn said it is making progress implementing default encryption of data exchanged with its users after a security company alleged some users are still at risk of account takeovers.
San Francisco-based Zimperium, a mobile security company, wrote on its blog on Wednesday that it is still possible to hijack some LinkedIn users' account networks using a technique called SSL stripping.
The technique involves a man-in-the-middle attack where a hacker is watching a victim's Internet traffic, which is possible in public places such as a coffee shop where the victim is connected to a Wi-Fi hotspot.
When a person attempts a SSL (Secure Sockets Layer) encrypted connection, the attacker "strips" out the https attempt, replacing it with an http connection, enabling the collection of the person's authentication credentials.
The attack is possible against LinkedIn because it doesn't fully encrypt an entire user's session over SSL. LinkedIn always initiates an SSL connection when a person submits their login credentials, but in some regions of the world, flips the connection to an unencrypted one over http.
LinkedIn said in December it was in the process of making all user sessions fully encrypted. That work isn't quite done yet, although last week it said all traffic served to U.S. and European users is now served by default over https. Since 2012, LinkedIn users have had the option of changing their security settings to full https, but many might not have known about the setting.
Moving to full https is no easy task, and LinkedIn described some of the challenges it was facing in a blog post in December. Among those issues were increased latency, support by various content delivery networks for https and scaling issues.
LinkedIn's upgrade is one many other services have made. Google offered full https connections as an option for Gmail in 2008, but two years later made it the default. Facebook moved its service to https by default in January 2011.
LinkedIn spokeswoman Nicole Leverich wrote via email that the issue described by Zimperium "does not impact the vast majority of LinkedIn members given our ongoing global release of https by default."
In the meantime, users should turn on full-site https by going into their settings, clicking on the "account" tab, then going to "manage security settings" and checking the appropriate box.
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