Podrobný popis zabezpečení je uveden v následujícím PDF:
http://www.teamviewer.com/products/TeamViewer_Secu rityStatement.pdf

Nějaké info je i přímo na domovské stránce:

Encryption

TeamViewer includes full encryption, based on RSA private-/public key exchange and AES (256 Bit) session encoding. This technology is based on the same standards as https/SSL and is considered completely safe by today's standards.

The key exchange also guarantees a full client-to-client data protection. This means that even our routing servers will not be able to read the data stream.

Access Protection

In addition to the PartnerID TeamViewer generates a session password that changes with every start of the software to ensure added prevention of unauthorized access to a remote system.
Security relevant functions like file transfer require additional, manual confirmation of the remote partner.
Also it is not possible to control a computer invisibly. For data protection reasons the person sitting on the remote computer has to be able to detect when someone is accessing the machine.

Code Signature

All program files are secured using VeriSign code signing technology. This allows you to verify the origin of the executables you received.
Even the QuickSupport Custom Design tools are dynamically signed during generation!