Discovery
The attack was first discovered by researchers Lenny Hansson and Kenneth Bjerregard Jørgensen at the Security Operations Center of the Danish Telecom operator TDC. The researchers' goal is to protect customers on that telecom network fromThe BlackNurse attack attracted our attention, because in our anti-DDoS solution we experienced that even though traffic speed and packets per second were very low, this attack could keep our customers' operations down. This even applied to customers with large internet uplinks and large enterprise firewalls in place. We had expected that professional firewall equipment would be able to handle the attack.
DOS attacks
Denial of service is typically accomplished by flooding the targeted machine or resource with superfluous requests in an attempt to overload systems and prevent some or all legitimate requests from being fulfilled. Commonly, such an attack is done in a distributed manner, where many clients will send requests to a given server. The sum of all the client's traffic is often enough to overwhelm the destination and cause the service to go offline or become unavailable.Attack
In the case of the BlackNurse attack, instead of flooding a remote system's internet traffic with superfluous traffic, the attack takes advantage of an imbalance between the resources required to send traffic and the resources required to process it. Namely, the BlackNurse attacks uses ICMP with Type 3 Code 3 packets. This is a packet that is meant to be sent when a destination's port is unreachable. Unlike previous attacks using the ICMP protocol-- Smurf attack, ping flood,Determining vulnerability
To test if your device is vulnerable, you can send the ICMP packet to your network usingReasons for efficacy
Because of the history of ICMP attacks, many ICMP packets are commonly blocked on firewalls. However some ICMP packets are necessary to allow the network to work properly. Destination port unreachable is one of those packets that is required. Typically however, an attack will only be effective if the incoming traffic is greater than the bandwidth of the victim machine. In the case of BlackNurse however, the attack takes advantage of the processing logic in many firewalls for handling this traffic. This attack is important because it leverages a necessary component of internet traffic and because it doesn't require the use of aImpact
Due to the low cost for the attack, because low bandwidth connections are common, this attack can be used very effectively. The original researchers at SOC TDC have noted that the attack is currently being used against clients on their own network.Origins of the name
The attack was named BlackNurse as a joke because two of its principal researchers were a former blacksmith and a former nurse. The media picked up on this name before it could be changed.References
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