Embodiments relate to detecting and mitigating network intrusions. Packets are inspected at their source/destination hosts to identify packet trends local to the hosts. The local packet trends are combined to identify network-wide packet trends. The network-wide packet trends are used to detect anomalies or attacks, which in turn informs mitigation actions. The local inspection may be performed by reconfigurable/reprogrammable “smart” network interfaces (NICs) at each of the hosts. Local inspection involves identifying potentially suspect packet features based on statistical prevalence of recurring commonalities among the packets; pre-defined threat patterns are not required. For network-wide coherence, each host/NIC uses the same packet-identifying and occurrence-measuring algorithms. An overlay or control server collects and combines the local occurrence-measures to derive the network-wide occurrence-measures. The network-wide occurrences can be used to automatically detect and mitigate completely new types of attack packets.