When Michael came out, a need to prevent message modification attacks was built into it. This method instructed the access point to deploy a feature called the TKIP countermeasure procedure. As a quick reminder, the process works by having an access point shut off if it receives two MIC failures in less than one second. When the access point shuts off, it will only do so for 60 seconds and then it will come up and require all of its new and previous users to re-key to gain access to the network. An attack was found in which an attacker could send corrupted traffic to the access point. This corrupted traffic would pass the WEP IVC and the frame CRC check; however, when it came to the TKIP examination, it would trigger the countermeasure. If an attacker did this, he could bring down the network until he was located and physically dealt with.
Sep 13
