[FD] IKE Aggressive Mode Downgrade Attack?

Hello I was reading about "ike aggressive mode with pre shared key" (CVE-2002-1623). As described by cisco (http://ift.tt/1IsApqk), this is still an issue "When responding to IPSec session initialization, Cisco IOS(r) software may use Aggressive Mode even if it has not been explicitly configured to do so. Cisco IOS software initially tries to negotiate using Main Mode but, failing that, resorts to Aggressive Mode." Are there known downgrade attacks? Counter-Measures? Thanks for your feedback and regards, mli

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