Poster: The Potential of Erroneous Outbound Traffic Analysis to Unveil Silent Internal Anomalies

Passive measurement has traditionally focused on inbound traffic to detect malicious activity, based on the assumption that threats originate externally. In this paper, we offer a complementary perspective by examining outbound traffic, and argue that a narrow subset --- what we term erroneous outbound traffic --- would suffice to discover a broad class of malicious, suspicious, and anomalous patterns. This traffic consists of packets sent by internal hosts that either receive no response, trigger ICMP errors, or are ICMP error messages themselves generated in response to unsolicited requests. To demonstrate its potential, we collect and analyse erroneous traffic from a large network, uncovering a variety of previously unnoticed issues, including misconfigurations, obsolete deployments, and compromised hosts.