Skype stores all application data in a local database in plain text

Romanian Researcher discovered that Skype application store sensitive User Data Unencrypted on a local database.

A Romanian programmer at Hackyard Security Group, Dragoş Gaftoneanu, revealed through a  blog post that the popular VOIP application Skype leaves its local database unencrypted.

Unfortunately the problem is very common, many applications, especially mobile apps, don’t encrypt application data exposing user’s information to serious risks for their privacy. 

According Gaftoneanu, all user data, including all Skype-to-Skype voice, instant messages, video and file transfers are encrypted, so it was normal to expect that also Skype’s local database is encrypted. Gaftoneanu discovered that Skype leaves users’ data, including full name, birthday, phone numbers, country, city and even full chat conversations in plain text on the systems’ hard drive in a known location.

This means that anyone accessing a user’s PC may gather application data stored always in the same location, it’s clear that cyber criminals may use them for various illicit activities.

The programmed, while he was chatting with his friend on Skype, noticed a folder in his Linux home directory that contains a database file named main.db. The expert has verified the anomalous implementation on Linux first, later it discovered same lack of encryption also on every operating system.

In Linux: /home/user/.Skype/skypename/
In Mac OS X: /Users/user/Library/Application Support/Skype/skypeuser
In Windows : C:\Users\Username\AppData\Roaming\Skype\skype.id

Gaftoneanu connected a SQLite utility to the unencrypted Skype database, discovering that its content was accessible without authentication. The tables in the main.db database scheme contain account information in plain text such as the Skype name, full name, birthday, country, city, mobile phone numbers, emails from Accounts and many other basic information.

In the above image is proposed the list of tables in the Skype database, the “CallMembers“ table is used, for example to store the information about when and whom user called. The ‘Contacts’ table stores the user’s contact list along with skypename, full name, birthday, country, city and phone_mobile.

The “Messages” table is used as a local archive for users’ chat conversations, also in this case the information is stored in complete, plain text format, the situation is the same for Videos and SMSs.

We can imagine various attack scenarios, for example, attackers can use a malware to steal the above information, to protect the user’s data, Gaftoneanu suggests to remove the content of main.db every time they close Skype application.

“Basically, anyone that has access to your laptop (even without root privileges), can steal your main.db file and see what you have talked, when you’ve talked and with who you’ve talked.”

The programmer also provided a Linux based script to remove main.db automatically, if users want to use need it they have to run it on every startup.

Let’s hope Microsoft Skype will fix asap the poor implementation.

Pierluigi Paganini

(Security Affairs –  Skype, Encryption)