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49.13.16.233 has a very high threat confidence level of 81%, originating from Falkenstein, Germany, on the Hetzner Online GmbH network (24940). It has been observed across 28 sessions targeting SIP, First observed on March 5, 2026, most recently active March 5, 2026.
Automated SIP OPTIONS requests used to validate reachable VoIP endpoints and enumerate service capabilities without initiating a call session. The client sends standalone OPTIONS probes with high-entropy or unusually long Call-ID values, a pattern commonly associated with scripted scanning frameworks or VoIP reconnaissance tooling. Such activity is typically observed during infrastructure discovery phases where attackers identify responsive SIP servers, supported methods, and potential targets for toll fraud, brute-force registration attempts, or later exploitation campaigns.