Disclosed are various embodiments for detecting and responding to attacks on a computer network. One embodiment of such a method describes monitoring data communications transmitted to a target class of first computing nodes; in response to detecting a non-legitimate data communication to a computing node in the target class, determining whether the non-legitimate data communication is a form of attack on a network to which the computing nodes are connected; and in response to determining that the network is under attack, implementing new security measures for second computing nodes that are not part of the target class to protect the second computing nodes against the attack on the network while the attack is ongoing.