![]() ![]() ![]() It has a main limitation: how can we define the threshold in a sensible way? This approach is very similar to the way alerts are created in a SIEM software like Elasticsearch or Splunk. Print("+ Create list of suspicious IP addresses. # extract the destination IP (device that sent the query) If packet.haslayer(DNS) and packet.qr = 1 and packet.ancount = 0: We can use Python and Scapy to try to detect these by counting the number of empty DNS responses received by each IP in the capture: from scapy.all import * This means a computer infected with a DGA malware will usually receive a lot of DNS replies that contain no answer (also sometimes called NXDOMAIN errors). However, most of these generated domain names have no corresponding DNS entry. b which, at first generated 250 domain names per day. The technique was popularized by the family of worms Conficker.a and. The large number of potential rendezvous points makes it difficult for law enforcement to effectively shut down botnets, since infected computers will attempt to contact some of these domain names every day to receive updates or commands.įor example, an infected computer could create thousands of domain names such as: and would attempt to contact these with the purpose of receiving an update or commands. If packet.hasLayer(DNS) Detection of domain generation algorithms (DGA)ĭomain generation algorithms (DGA) are algorithms seen in various families of malware that are used to periodically generate a large number of domain names that can be used as rendezvous points with their command and control servers. For example, to process only DNS packets: from scapy.all import * Therefore we can use the method packet.hasLayer(protocol). Next, we will typically filter packets depending on the payload protocol. # it does NOT load the complete file in memory ![]() Moreover, you can use the method packet.show() to show the list of available protocol layers and values: from scapy.all import * You can do this with PcapReader, which actually create a generator. The first thing you want to do is open a pcap and loop over the packets. You can install Scapy using PIP: pip3 install scapy Read a PCAP In this blog post we show how Scapy can be used to read a pcap file, in order to detect abnormal behavior. Scapy is a wonderful Python library that allows to craft packets and send them on a network. ![]()
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