This disclosure generally relates to the generation of a packet signature for packets determined to correspond to a network attack, such as a denial of service (“DoS”) attack. Specifically, a set of data packets captured during normal system operations can be analyzed to determine a set of baseline attributes. Additional packets captured during an attack can be compared to the baseline attributes, to determine, for individual packets, a probability that the packet forms a part of the attack. A packet signature can then be generated to identify attributes that are characteristic of the attack. That signature can then be used to filter out packets and mitigate the attack.