[SIPForum-discussion] SIP Security

[Nguyen Duc Hoang]

Hi,everybody!

When Subscriber A calls a SIP call to Subscriber B. 
A                                MiM                               Proxy
---------------------INVITE---------------------->
<----------------------401-------------------------
-------------------------ACK--------------------->
<--------------------INVITE(credentials)----------
     one week later           ---INVITE(credentials)-->
                                      <-----100trying-----------
                                      <-------180 ringing-------
                                      <-------200OK----------
                                      --------ACK------------->

A MITM captures all messages from A then uses its parameter to take an unauthorized call. I don't know how he can captures all messages (In real conditions - because i read that threat in a document about AT&T network). I also don't know what fields does he have to take information, why must to be that fields and why the attacker can be accepted by the proxy after 1 week?

Can you explain it for me?



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