I've noticed that ekiga [...], from its first run,
with default configuration, uses a public STUN service at stun.ekiga.net.

The purpose of that service is to inform the client of its public IP
address in case it is behind NAT.  That address is given out by the
client when establishing outgoing SIP calls.

It occurred to me that if the stun.ekiga.net service, or its DNS
servers, were compromised (or operators untrustworthy), it could instead
return to a particular client the IP address of a host controlled by the
attacker.  That host could proxy SIP connections back to the legitimate
address of the client, and thus be in a position to intercept calls.

This is even documented in RFC 3489 section 12, "Security
Considerations" as "Attack IV: Eavesdropping".

The use of this particular STUN service is configurable through
gconf-editor, however it isn't even indicated to the user within ekiga.

Moritz Mühlenhoff <jmm@inutil.org>, nov. 2012
