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Event ID: 16435 Source: LiveCommunicationsServer

Level
Description
At least one invalid authentication signature was detected. There were <value> messages with invalid signatures in the last <value> minutes. The last one had the FROM header: sip:username@domain.com. This could be due to a client or server which is not handling authentication correctly or it could be due to an attacker.
Comments
 
We have seen this in Live Communication Server 2003 because a user is logging in on a computer that is not part of our domain. The user usually logs in via VPN but his massager tried to log in before the VPN was connected. Eventually the user was able to log in after the VPN was established.

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