1. A method comprising: receiving, by a packet-filtering system configured to filter packets in accordance with a plurality of packet-filtering rules, data indicating a plurality of network-threat indicators; and configuring, by the packet-filtering system, the plurality of packet-filtering rules to cause the packet-filtering system to: identify packets comprising unencrypted data; identify packets comprising encrypted data; and determine, based on a portion of the unencrypted data corresponding to one or more network-threat indicators of the plurality of network-threat indicators, that the packets comprising encrypted data correspond to the one or more network-threat indicators.